Final Pennsylvania Updates

Clinton has increased her lead in the trend estimates over the course of the last polls to 6.6 points using the standard estimator, and to 8.4 points using the sensitive estimate. Last minute polls have given her bigger margins.

Now the key question is whether undecideds push her over a 10 point win, or whether increases in turnout by new "unlikely" voters raises Obama's total.


















Still a good bit of variation and some pollsters see a strong trend, others not so much.


















Pollster variation doesn't make a lot of difference in our trend estimates.

But remember, since the polls don't allocate undecided, both they and the trend estimates are leaving some 8 percent of voters on the table. They will go somewhere, and if they break disproportionately for Clinton you have a "huge win", while if they go overwhelmingly for Obama you have a nail biter or a dramatic come-from-behind win. In previous primaries, the "winner" has usually enjoyed a significant increase in support beyond what the last polls showed.

Pennsylvania Undecided Voters

Senator Clinton currently holds a 6 point lead over Senator Obama in Pennsylvania, based on our Pollster Trend Estimate, 49%-43%. But that leaves about 8 percent undecided. What they do will determine whether Clinton's vote expands her lead compared to the polls, or if the undecided narrow or possibly reverse, the lead.

My partner at Pollster, Mark Blumenthal, has looked at this using aggregate polling data here and in his NationalJournal.com column here.

In this post I take a look at the individual level, though using data that are three weeks old, so use caution in extrapolating to tomorrow's electorate.

Using data from the Time/SRBI poll of Pennsylvania, conducted 4/2-6/08, I estimate a model of support for Obama compared to Clinton. I use "the usual suspects" as variables predicting vote: partisanship, gender, race, Hispanic ethnicity, region of the state, age, education, religion and income. The data at that time found an eight point Clinton lead, a bit higher than today's trend estimate.

Using the coefficients for "decided" voters, I can estimate the probable vote of the undecided 11% of voters in the poll. This gives us a look at how they would be expected to behave IF they behave like those who have already picked a candidate. (Note the "if" here. As with all models, this assumes stable influence of the variables among the undecided as among the decided.)

The plot above shows the distribution of estimated probability of voting for Obama. Values close to zero are very likely to support Clinton, while values close to 1 are very likely Obama supporters. Those close to .5 are flipping a coin. The shape of the distribution gives a sense of where voters "lump up" in their estimated preferences.

The black line plots the distribution among those who reported a vote preference. The red line plots the distribution of estimated support among those who said they were undecided in early April.

The key point is that the undecided resemble the decided, with a small shift to the left, suggesting they were as a group somewhat more likely to support Clinton. In these data, the primary difference between undecided and decided voters was age, with older voters more likely to say they hadn't decided. As we've seen in virtually every exit poll, older voters are more likely to support Clinton, so the result we find here, that the undecided lean a bit more towards Clinton, is consistent with this result.

Now again for the caveats. These data are three weeks old. The model requires the assumption that undecided voters ultimately behave like those who decided. Different variables as predictors can make a difference. And so on.

The goal here is NOT, NOT, NOT a prediction of tomorrow's vote. Much may have changed since the first week of April.

The point is to illustrate what we can learn about undecided voters beyond the simple fact they say "undecided". In this case, the data suggest they are not wildly different from those who decided, but their older age makes it more likely they ultimately lean more to Clinton.

The Time/SRBI data are archived at the Roper Center for Public Opinion Research. I am solely responsible for the analysis here.

Pennsylvania Pollster Comparison

Judge for yourself.

Day Before Pennsylvania Sensitivity Update

The Pennsylvania race has turned slightly toward Clinton over the weekend, with her lead now at an even 6 points in our standard trend estimate. If you believe in taking more chances with random noise, the sensitive estimator has a 6.4 point Clinton lead.

In the rush of new polling over the weekend, it is also good to check how much any of them may be affecting our estimates.


















Dropping any single pollster makes only a bit of different to our estimates. The Clinton trend ranges from 48.5% to 49.6%, while Obama ranges from 42.6% to 43.5%. So dropping your least favorite pollster can, at most, account for the difference in a 5 point race and a 7 point one.

And note that we still have about 9 percent undecided. I wonder what they will do?

National Dem Trends, Newsweek Poll

A new Newsweek poll gives Barack Obama a 54%-35% lead over Hillary Clinton among Democratic voters (story here, detailed results here, and thanks to Newsweek and their pollster, Princeton Survey Research Associates International, for a full and complete disclosure of the details of their survey. A model others should be encouraged to follow.)

The Newsweek poll raised a few eyebrows for its 19 point Obama lead, considerably more than other recent polls, and beyond the 10.4 point Obama lead in our trend estimator. However, a closer look at recent data shows that Newsweek is not far from other recent data. Newsweek is the 6th poll in April with Obama at or above 50%, while five April polls put him below 50%. With Clinton, Newsweek is the 4th April poll putting her at or below 40%, while eight polls have her above 40%. So Newsweek shows a larger Obama lead than others, but it is not as far out of line as may first appear. (Note in the counts of polls above, we only count independent samples of the Gallup daily tracker, so dont' count each of their daily results as new polls.)

As you can see from the plots below, we've not seen many recent outliers in the national Democratic nomination polling, and the new Newsweek is well within the 95% confidence interval.






















All that said, our trend estimate for the race puts Obama at 50.2% and Clinton at 39.8%, a significant gain for Obama during the month of April. Since late March, Clinton has suffered a somewhat greater downward slope while Obama's gains have been a bit more shallow, implying a slight gain among undecided voters.

The Newsweek poll also has some interesting internal results. As with virtually all this year's polling, Obama has a substantial lead among Independents who will vote in the Democratic primary or who lean Democratic: 61% to 28% for Clinton. What is a key to Obama's strength in the Newsweek poll is he ALSO leads among self-declared Democrats 51% to 38%, a group Clinton has won in most contests. If real (and I want to see more data before I accept this change) then Obama may be winning the consensus among party rank and file that will be key to persuading Superdelegates to move strongly in his direction. So long as he trails among the strongest party identifiers, that case is less persuasive. Pennsylvania provides a new test of this possible change in support. (Obama continues to trail in our Pennsylvania estimates, so it is unlikely he has so far persuaded a majority of Democratic identifiers there, though stay tuned for Tuesday's exit polls.)

The other important shifts in this national Newsweek poll is that Obama leads among men 57%-31% but also among women 52%-38%. Again this would represent an important gain among women.

The age gradient in Obama support has been interesting all year. In the Newsweek poll, he wins 18-39 year olds by 62%-28%, as usual, but also wins 40-59 year olds by 54-36%. In past exit polls, his "break even point" has varied among age groups from as low as 40 (i.e. losing all groups over 40 years old) to as high as 59 (only losing those over 60 years old.). More astonishing here is he gains a plurality of those over 60, 47%-41%, which if true would be his best performance among older voters all year.

The area of the Newsweek poll where Obama still suffers is among working class or poor whites, where he trails badly, 35%-54%. In contrast he leads 52%-35% among upper and middle class whites. That class divide remains a critical issue for his campaign.

A caution here as well. In any poll with such high overall support, the support almost has to reach across many subgroups (not quite as a mathematical certainty, but as a strong empirical regularity.) So we should be careful not to accept the depth of Obama's support among Democrats, women and those over 40 years old until we have more evidence from additional polling. In the exit polls this year, where we see big Obama wins (VA, MD, WI) we also saw him making strong inroads among these groups. But with the margin he achieved in these states, it would have been hard NOT to have done well across groups. Be careful of the cause and effect attributions here. It is a challenging state like Pennsylvania that can reveal how deeply into the various demographic groups Obama has managed to extend his appeal. But with those cautions, Newsweek's poll shows some evidence that the national Democratic constituency is moving in his direction across a number of groups.

If these changes are real, we'll see new polling that reflects it. If just a favorable poll (though not an outlier!) then new polling will show that these groups are not quite as enthusiastic for Obama as the current poll suggested.

Pollster Effects on Pennsylvania Trends

There is a lot of interest in the differences among pollsters, and especially what effect they have on the perception of the race. Here at Pollster, the interest is specifically on the question of whether individual pollsters drive our results, and if so by how much.

So here is a quick look at those effects in Pennsylvania's Democratic primary.

The chart above shows the trend estimates that result from dropping each pollster in turn, and reestimating the trend without that pollster. This is a specific test of how much it matters whether we include a particular pollster or not.

Over the 15 pollsters we have represented in Pennsylvania, the estimates excluding each one for Clinton range from 46.6% to 48.3. The estimate with all pollsters included is 47.4% for Clinton.

For Obama, the estimates range from 41.2% to 42.5%, with the estimate for all pollsters at 42.0%.

The upshot is that pollsters do matter, but none drive the results by very much. A 1.7% range on Clinton and a 1.3% range on Obama for the trend estimate is very small compared to the range we see across the raw poll results. Another example of the greater stability of the trend estimators we use compared to the substantial variability across polls.

We can look at the effects of each pollster by comparing the trend estimate without that pollster to the estimate with them. The higher the effect, the more that pollster drives our trend estimate up for that candidate. Negative effects means the pollster drives our estimate down. Again, this is compared to the trend with and without the individual pollster.

The two charts below show these effects for Clinton and for Obama.


















For Clinton, SurveyUSA has the highest positive impact on our trend estimate, followed by Rasmussen. At the opposite end, PPP has the largest negative effect on our trend, with Zogby/Newsmax the next largest negative effect. Other pollsters are clustered rather closely around zero.

And it is important to note that even the four largest positive and negative effects are all less that 1 percentage point.


















For Obama's trend, Quinnipiac shows the largest positive effect, followed by Zogby and PPP with near identical effects. On the negative end, SurveyUSA has the most negative effect of Obama trend. Again, none of these effects is as much as one percentage point, and SurveyUSA's is less that half a percentage point. Other pollsters have less impact.

We can also look at the joint effects. These are the same as seen individually above but plotted against one another.


















Pollsters do matter, and outliers matter even more. But the net effect of any individual pollster on our trend estimates in Pennsylvania are modest, especially when viewed in comparison to the wide range of raw poll results for each candidate. Another advantage of combining information across polls rather than pick single polls we "like".

Pennsylvania Dem Sensitivity Comparison

Here is an update on the Pennsylvania Trend Estimates for both the standard estimator and the more sensitive one.

The difference is small: 0.3 for Clinton and 0.8 for Obama. But hey, it can be a game of inches. Either way it looks like about a 5 point margin right now.

(See earlier posts for details on the standard and sensitive estimate. The sensitive is about twice as responsive to the data, but tends to chase ghosts.)

Pennsylvania Dem Trend Sensitivity

Time for a look at the sensitivity of our trend estimators. ARG has a new Pennsylvania poll out showing a 20 point Clinton lead. But Susquehanna Polling has one completed three days earlier with a 3 point Clinton lead and Zogby has one on the same day with a 4 point Clinton lead. Did things shift that swiftly or do we have an outlier?

Our standard trend estimator is designed to resist outliers, and it manages to do so in this case (see the chart above.) With or without ARG (and with or without ARG AND the close Susquehanna poll) the trend estimates only change by 10ths of a percentage point. What does change slightly is the slope of the trend estimate between the solid line with all polls and the dashed and dotted lines without ARG and without ARG and Susquehanna. In fact, the changes are slight enough you need to squint to really see them.

It may surprise you that removing ARG makes Clinton's trend estimate go UP, when you would understandably expect it to go down. The reason is simply that she is trending down either with or without ARG. Removing ARG means that the latest poll for the trend estimate is 3 days earlier, hence higher up on the downward trend. Since ARG doesn't much affect the slope, removing it just "backs the trend up" by three days, making Clinton a tiny bit better off. The same happens in reverse for Obama-- without ARG he is a shade worse off (0.1 percentage points) because his trend is rising either way, so backing up 3 days hurts him a tiny bit. (Removing ARG and the close Susquehanna poll makes similarly modest changes to the trend estimate.)

So for our standard estimator, whether we include or exclude the latest ARG poll makes very little difference.

That is by design. At this point a single new poll that shows a big change should be regarded with caution. It MAY reflect a big shift over the weekend. But it could just as easily be a statistical fluke that will not be replicated in other new polls. Until there is more evidence one way or the other, the trend estimate is designed to not chase after a single poll far away from the other data. But if we get two or three more polls showing similar results, the trend estimator will then be convinced the shift is real, and will turn in the direction of the new data.

But what if we decided to be less cautious and more willing to respond to new polling? For that, we have an alternative estimator that is about twice as sensitive. This one will pick up new trends much more quickly, but will also be misled by a single outlier much more easily. Let's see what this more sensitive estimator thinks is going on.

















With the sensitive estimator, the ARG poll makes a HUGE difference. It shifts the difference in trends from a 4.3 point Clinton lead to a 12.6 point lead! That is really responsive. But it also demonstrates what a large difference a single poll can make when we crank up the sensitivity of the trend estimator.

What is more interesting with the sensitive estimator is that taking out ARG, we see a flattening of Obama's trend and even a tiny downturn, though also a continued decline for Clinton. If we also take out Susquehanna we find Obama continuing to rise but Clinton falling at a slower pace than without ARG alone. (You really have to squint to see the dotted line. Sorry about that.) Clinton leads by 4.2 without ARG AND without Susquehanna, by 4.3 without ARG alone.

So perhaps the sensitive estimator is showing us something new-- Obama may have flattened or even turned down a shade recently, but if so Clinton seems to have continued to decline as well. This also illustrates why we prefer our more conservative estimator. The sensitive version is just too dependent on individual polls at the end of the series. It provides a possible early hint of things to come, but is too unstable to count on. Our standard estimator may be a little slow to pick up a change of direction, but it seldom chases after random noise.

As for ARG's result, let's wait a day or two and see what other polls have to tell us and how our estimator responds.

For an animation of the Pennsylvania sensitivity analysis for a wide range of sensitivity, download this Acrobat file and use the arrow keys to control the animation speed.

Bush Approval Falls to 28.3%

President Bush's approval trend has taken a sharp downturn in recent weeks, to fall to a new low for the administration at 28.3%. This follows a lengthy period of stable approval at around 32-33%.

Recent polls from Gallup and AP/Ipsos put approval at 28%, a new low for the Gallup poll. Harris recently found approval at 26% while CBS News put approval at 28%. Pew similarly has approval at 28%, though the Diageo/Hotline result for registered voters (as opposed to adults in the other polls) has approval at 35%, the only recent poll over 30%.

While the President has taken a back seat to the primaries in recent months, his new approval slump reflects growing pessimism over the economy which has displaced the war in Iraq as the most important problem facing the country. Likewise the percent saying the nation is headed in the wrong direction has continued to grow in recent months, to a high of 81% in a recent CBS News poll.

Most Important Problem, 2005-2008

The Iraq war and the economy have consistently been the top two "most important problems" facing the nation during President Bush's second term. But the dynamics have changed dramatically over the past seven months.

After near parity in 2005, the war dominated throughout 2006 as far more important that the economy, and with rising numbers of people citing the war as most important. That peaked in early 2007 with concern over the war gradually diminishing through most of the rest of the year.

And then the economy struck. As recently as August 2007 only 8% said the economy was the most important problem. By early September that jumped to 13%, then to 23% in January and now 37% in early April. By contrast the war fell from 34% to 15% over that same time.

It will be ironic if the fall campaigns largely ignore the war to focus on an economy that 12 months earlier had looked fairly good.

California Super Tuesday Pollster Comparison

There is quite a bit of disagreement in the California polls, so let's do a Pollster Comparison to see who says what.

The Democratic race has the biggest gap across pollsters. Most see Clinton ahead, but disagree on how much the race has tightened. But Suffolk and Rasmussen put Obama just barely ahead in their final polls. And the big difference is in the Zogby/Reuters/C-SPAN poll that sees Obama not only ahead but expanding his lead to double digits.

That gives us a range of results from Obama ahead by more than 10 to Clinton ahead by 10. Somebody is not quite right here. But who? And why?

Across all the polls, Clinton is relatively flat while Obama has gained. But looking at each poll and each candidate reveals more differences across pollsters.

Both Zogby and the Field poll find some decline for Clinton while others have her flat or rising (SurveyUSA and Rasmussen).






















Everyone sees Obama either flat or rising, with no pollster (who has at least 2 polls) seeng Obama declining. But the extent of the rise, and how high Obama's starting point was, differs quite a bit across pollsters. Survey USA and Rasmussen both see Obama gains, but SurveyUSA offsets that by measuring gains for Clinton as well, resulting in relatively little net change over their last three polls. Rasmussen, on the other hand, has Clinton gains but even bigger Obama gains, resulting in a net decline and a final poll with Obama just barely ahead.






















The Zogby polls in contrast find both Clinton declines AND Obama gains, making for a net change that strongly favors Obama and results in his 13 point lead in the final Zogby poll for California.

On the Republican side, we also see substantial differences. Two pollsters see a dramatic tightening of the race. Rasmussen and SurveyUSA estimate that McCain's earlier lead has now collapsed to a dead heat. (A single ARG poll also sees a dead heat, but has no over time data for comparison of trend.) In contrast the LA Times/CNN/Politico and Field polls both find McCain gaining some ground in their polls. These two are a bit stale now, but showed gains even when Rasmussen and SurveyUSA saw declines, so this is not only a difference of survey dates.

Zogby/Reuters/CSPAN is again quite different, finding Romney leading in all three polls and expanding his lead to high single-digits in the last two polls.























Across the Republican polls, the differences are almost all matters of the degree of increase for both McCain and Romney. All polls agree that McCain has been increasing his support. But they also agree that Romney is rising sharply. The differences in net support have a lot to do with differing estimates of how fast and how far Romney has risen. Those with the greatest Romney rises have him catching McCain or leading him.

Given the length of time it is likely to take to count the California vote, it may be Thursday before we know which of these polls was closer to the end result.

Super Tuesday Endgame

Updated: 2/5/08 at 1:59 pm est


















Now that the first "Super" event of the week is over, time to turn to the next one.

We've got a number of polls in several states, fewer polls in others. Here are the trends in the 17 states for which we have polls since January 1.

In the Republican chart below, I've omitted Utah where Romney holds an 84-4 lead over McCain, according to the one Republican poll since January 1. Expanding the scale to include that data point makes it hard to see the differences in all the other states.

See the individual state charts at Pollster.com for trend estimates in the states with sufficient polling. Here, look at the data and reach your own conclusions. The data here are through Sunday. I'll update the charts Monday evening with the Monday polls.

Super Tuesday Polling at a Glance

Updated: 2/5/08, 1:58pm est













































No time for commentary this morning, so here is an explanation.

It is ironic and annoying that the most important date on the primary schedule is also the date with the fewest polls per state. Just as the campaigns are struggling to run 22 simultaneous campaigns, so pollsters and the media have invested little in comprehensive polling of the Super Tuesday states. Even large states such as New York and California have fewer than 10 polls since January 1, far fewer than we saw last week in Florida for example. As a result, we have many states with no data at all, preventing a comprehensive overview of the prospects for Tuesday. Even where we do have polls, we lack enough to consistently estimate the trend with data taken since Iowa. Where we can estimate trends, we've done so on the "regular" state pages at Pollster.com. You should go there for the best trend estimates we can manage with so little data.

The charts here are a way of seeing the entire set of Super Tuesday states (where we have polling) at a glance.

Rather than plot the usual trends with so few data points, each poll is a point and the darker the point the more recent the poll. The points are also scaled in size to be proportional to the number of delegates at stake in the state.

Instead of a trend estimate, this plot highlights the median of all post-Iowa polling in the state. The shading of points will then let your eye tell you whether there is a visible trend around that median. Be your own data analyst!

When more states become available, they'll be added to updated charts. If a state is missing, we don't have polling for it. (If you think we've missed a state with polling data, let us know!)

Florida Republican Poll Errors

Polling had a pretty good night in Florida on Tuesday. While early polls understated both McCain and Romney's vote, the polls got better as election day closed in, reflecting a (measured) upward trend in both candidates support. By the last day or two of polling most polls were within the ten-ring, and a number were close to the five-ring.

There was more disagreement among the polls as to who was ahead, and this included some late polls that put Romney ahead of McCain. However, most of these polls reflected a race "too-close-to-call", rather than egregious errors about the leader, with one large exception towards the lower right in the plot.

As we've seen all year, the polls got the vote for third and fourth place finishers very accurately, almost all within the five-ring.

Florida Republican Endgame

The polls in Florida point to a very close contest between Mitt Romney and John McCain. As of Monday's polling used here (there will be new final polls available Tuesday morning) Romney has a small lead based on our trend estimators (both standard and sensitive). But that lead is so small that a "dead heat" is probably still a good characterization of the race.

As we've seen in several previous states, the final vote has often broken strongly in favor of the winner with little going to the second place finisher. But who will that winner be? Other than our trend estimates, the data have little more to tell us on that score. With Ron Paul polling consistently at between 4 and 5 points, there are at least 10% of voters yet to make up their minds. A strong surge could boost one of these front-runners from about 30% to near 40% and a very significant win. An even split of undecideds will make for a close finish with both around 33-35%.

Both Romney and McCain have been gaining ground in Florida, but Romney's rise has been consistently sharper than McCain's. Moreover, there is little evidence that McCain has enjoyed a post-South Carolina spurt in Florida. Nor does Romney's Nevada win seem to have helped him beyond his already considerable upward trend.

As the Florida race narrowed to a two way contest for first place, Giuliani and Huckabee have subsided into the 12-15 percent range. They too could go either way for 3rd and 4th, though at the moment Giuliani has a small advantage for third place. As mentioned above, Ron Paul trails with 4-5% for fifth place.

The chart below shows how much the polls in Florida have overlapped since the South Carolina primary and Nevada caucus 10 days ago. While the trend estimates are slightly distinct, the huge overlap of polls for Romney and McCain show that we should remain quite uncertain as to who is "really" ahead. Sometime Tuesday night, we'll find out.

South Carolina Poll Errors

The polls had a bad day on Saturday in grossly underestimating the support for Barack Obama, though they nailed the Clinton and Edwards votes quite well. Not one poll came within the ten-ring, and the final poll of the primary understated Obama's vote by nearly 15 points. Several polls flirted just inside the 20-ring, and one hapless example of the consequences of poor question wording, the Clemson University poll, understated Obama support by nearly 30 points. The Clemson poll allowed 36% to remain "undecided", hopelessly biasing downward their estimates of candidate support, but especially so for Obama.

My colleague Mark Blumenthal has posted a nice comparison of these South Carolina results with those "terrible" polls from New Hampshire. Below is the same poll error chart for New Hampshire, but scaled the same as the one for South Carolina above.























The New Hampshire results were mostly inside the 10 ring and all were inside the 15 ring. And a couple even touched the 5 ring. Judged by distance from the bullseye, New Hampshire doesn't look that bad, certainly not compared to South Carolina.

But there is another difference, and this is where New Hampshire was terribly wrong and South Carolina not so bad: All but one of the New Hampshire polls had the wrong leader. None of the South Carolina polls, not even Clemson's, got the leader wrong.

So while the distance from the bullseye was quite a bit worse in South Carolina, the creation of confounded expectations was not. It was the expectations that were created and then confounded that make New Hampshire a polling disaster, while there has been little said about the polling errors in South Carolina. (Except here, where we care about such things all the time!)

The other interesting comparison is the parallel that the number 2 finisher in both South Carolina and New Hampshire was quite well estimated. The SC polls got Clinton within normal margin of error. And the New Hampshire polls also got the 2nd place finisher there, Obama, within reasonable error.

The problem in both cases is in the substantial underestimate of the first place finishers vote. The final choices of late deciding voters is a challenge for all polling, and perhaps especially so in primaries where there is no "party identification" to come home to if you can't make up your mind. In New Hampshire the Clinton win rested on significantly more voters supporting her than expected. In South Carolina is was the magnitude of the victory, rather than first place itself, that confounded the polling.

Increases in voter turnout in this cycle may be part of the story (a 75% increase in South Carolina), but here we see those late deciders breaking for different candidates, and yet in both cases for the ultimate winner. Second place results may on average be slightly low compared to the polls, but the first place "bonus" seems quite strong. At least for the Democrats. In the Republican South Carolina primary, both first and second place finishers were a bit underestimated, so there was not the same asymmetric error for first place. The New Hampshire Republican race also about equally understated the votes for first and second. The relatively lightly polled Michigan Republican race shows somewhat greater underestimate of first place (Romney) and second place (McCain). And in Nevada, with only 3 late polls, Romney was dramatically underestimated, while Ron Paul finished second but was only moderately underestimated.

So perhaps these reflect pollsters' difficulty in discerning the likely behavior of undecided voters, or perhaps these are last minute decisions to vote by "not-so-likely" voters who are screened out of the sample but who turn out for the ultimate winner in larger than expected numbers.

Turning to 2nd and 3rd place, the chart below shows that the polls had a pretty good day predicting the Clinton and Edwards votes. Despite some chatter about a late Edwards surge and a Clinton fall (including some evidence in our sensitive trend estimates that such a movement was occurring) most of the late polls were within the five-ring for 2nd and 3rd place, and all got the order of finish right.

South Carolina Democratic Endgame

The South Carolina polling continues to show a substantial lead for Obama, while Edwards' rise hints that he could challenge Clinton for second place.

At the moment, Clinton continues to hold a six-point advantage over Edwards, but Edwards has been rising while Clinton has been moving down. Obama, meanwhile, has been fairly steady at around 40-44% support, though with some hint of a small decline in the sensitive estimator. Note however that the Clemson University poll included here had an amazing undecided rate of 36%. That makes every candidate in their poll look lower than in all other polls that have a much lower rate of undecided. The level of undecided is quite sensitive to how the poll is conducted, including whether respondents are pushed as to whether they "lean" towards a candidate. The Clemson poll apparently didn't push at all among undecided voters. We'd be making a mistake to read their data as indicating a decline of support for anyone.

A second place for Edwards would, of course, be good news for his campaign, while Clinton would no doubt argue she had conceded the state to account for a third place finish. But Edwards still has some ground to make up, and late deciding voters remain an unknown-- if they are unhappy with either Clinton or Obama, Edwards can benefit simply by not being one of them. This may be especially true among independents who vote in the Democratic race, and the expected handful of Republicans who show up. (Republicans and independents can vote in the Democratic primary only if they did NOT vote in last week's Republican primary.)

I think the more compelling story of South Carolina will be the exit poll results. Obama has appealed to white voters in previous primaries and caucuses. The pre-election polls have found him getting as low as 10% of the white vote in South Carolina. The potential for racial polarization in this Southern state could damage his ability to transcend race as a basis of voting. Paradoxically, there has been speculation that Clinton can win the votes of black women, a result that could reduce polarization in the exit poll. We'll know much more about how voters decided by Saturday night.

South Carolina and Nevada Poll Errors

Polling for the South Carolina Republican primary mostly got the winner right, but large undecided percentages prior to the election accounted for a general underestimate of the final vote for both McCain and Huckabee. Late polling also found the race closer than the eventual outcome.























Pollng for third and fourth place was less successful in detecting Fred Thompson's final strength and the drop of support for Mitt Romney, who abandoned South Carolina to spend time in Nevada, where he scored a strong first place finish. While almost all the polls finished inside the "5-ring", correctly seeing a close fight for the 3-4 spots, all but one poll got the order of Thompson-Romney wrong (and the one that got that order right substantially missed the magnitude of both votes.)























In the Nevada Republican caucuses the polls wildly underestimated Romney's final strength of 51% of the vote. (Note that the rings here have to be rescaled to include the very large errors.) Even the best of the three Nevada polls was more that 15 points off on Romney. The earliest of the three polls, taken before Romney's win in Michigan, was over 30 points low.

McCain and Huckabee ignored Nevada, essentially conceding the state to Romney, but the polling still failed to pick up the magnitude of his support there.

The polling likewise failed to capture Ron Paul's second place strength. Preelection polls put Paul at about 7% compared to his finish of 13.7%.























In terms of erroneous expectations, the polling also put McCain well ahead of Paul, uniformly getting the 2nd and 3rd place finishers wrong.























On the Democratic side, the final poll was inside the "10-ring", and the polling improved as the caucus approached. Here the surprisingly poor showing of John Edwards, and the Democrat's caucus reallocation rules for non-viable candidates helped boost the final percentages away from the polls. The three most recent polls all got the order of finish correct.

South Carolina Republican Endgame

South Carolina is looking quite interesting for the Republicans. There has been a decent amount of polling since Iowa, with Huckabee getting a brief bounce but subsequently subsiding a bit, while McCain has gained since the first of the year. There is little evidence that Romney benefited significantly from his Michigan win. Fred Thompson has risen a bit, based on the sensitive estimator, but still trails in fourth place.

If we try to pick these data apart a bit, the sensitive red estimator is trying hard to fit Huckabee's varying fortunes. His December rise, and Iowa bump are picked up, but if those were real then so is the decline we see to his current level of about 22%. Whether he has been trending up down, or flat depends on how wide your view of the polling is. The blue estimator has the longest run view, and still see's him improving over his showing in 2007, but that was ages ago politically. The sensitive red estimator is showing a downturn since Iowa, but if you squint hard and ignore the earliest post Iowa polls you might believe you can still see some rise in the last week or 10 days. But do note the bottom line: the two different trend estimates still put his current support at between 21.6% and 23.3%. So while they disagree on immediate trends, the end up close to the same bottom line.

For McCain, there is little dispute that he has surged since early December when he was in the low-teens to somewhere in the mid-to-upper 20s today. The sensitive estimator thinks the rate of climb since Iowa has been more rapid that does the blue estimator, but again both put his support between 26.9% and 29.3%.

One big question in South Carolina is whether conservative criticism of both Huckabee and McCain is having any effect. If Thompson is benefiting from that, his polls only modestly show it. The sensitive estimate suggests a rise from about 10% to about 14%, but there is no polling evidence for a surge that would allow him to compete for first place.

Finally, Romney's Michigan win seemed to help him in Nevada (based only on 3 polls, I should add) but there is no evidence of a bounce in South Carolina. After spending Wednesday and part of Thursday in the state, Romney appeared to concede the race and moved on the Nevada to campaign, where his chances look better. The Romney trends are also in complete agreement: No substantial trend, and both agree on 16%.

One big warning here. South Carolina has shown suprising numbers of undecided. The Fox poll today, for example, has an unbelievable 19% undecided. That is HUGE. And, if you add up the trend estimates for the four top candidates here, you get... 81% leaving the same 19% unallocated. In Fox's poll, less than 10% pick Paul, Giuliani or Hunter combined, so there is a gigantic amount of room for those last minute deciders to break one way or the other.

With a history of under-the-radar negative campaigning in the state, and evidence of the same this year, it would be surprising if we don't see some important shifts here at the end.

In New Hampshire and Michigan, those late shifts have benefited the first place finisher disproportionately.























This chart is an attempt to illustrate the variation in the polling over the past week. (A comment raised some good questions about it, so let me try to explain it better.) The horizontal axis is the current sensitive trend estimate for each of the top four candidates. The vertical axis is the actual poll results since the Michigan primary. The point is that the sensitive trend puts the order as McCain, Huckabee, Romney and Thompson. But the vertical spread of the points for each candidate shows how much variation we've see from poll to poll. While most of the McCain polls are higher than most of the Huckabee polls, there is some overlap. Likewise most of Huckabee's results are higher than Romney. But Romney and Thompson show considerable overlap. The less the overlap, the more reasonable it is to believe the separation between candidate trends is reliable, and the more overlap the greater the uncertainty. If all the polls showed exactly what the trend estimate shows, then the points would all be on the diagonal line, and there would be no disagreement at all. The fact that most of McCain's polls are below the 45 degree line shows that he has been trending up, while Huckabee's points are mostly above the diagonal, consistent with his recent downward trend. Romney and Thompson are about equally above and below the diagonal, showing little trend over the last eight polls since Michigan.

But the simple point is that the more spread you see vertically, the more uncertainty. And the more overlap between pairs of candidates, the more uncertainty.

For me, that 19% undecided in the Fox poll is scary. And fun!

Nevada Endgame

The Nevada caucuses are upon us, but the polling is scant. As the graphs make clear, we have only four polls since New Years, so the trend estimates here should be taken with more than the usual grain of salt. With just 4 polls, the sensitive red estimator is going to try hard to come close to all the polls, making Clinton and Edwards look like they are experiencing huge trends. Obama's four polls are more clustered, so the red trend is a little better behaved, but still tries hard to find a trend when there truly isn't enough data to support one.

Also, there was no Nevada polling between December 3 and this week, so we have NO IDEA what happened during that time. Both trends are fit to all the data (including polls in 2007 not shown in the plots.) So the blue line is the best conservative guess given all the data in 2007 plus the four polls in 2008. The red line sensitive estimator is, in this case, I think hopeless.

If you force me to choose, I'd take blue in this case. With so little data, you want to be conservative. But you can see the poll-to-poll variation is large for Clinton and Edwards. Perhaps a lot has been changing this week, but you can't be sure it isn't just pollster variation.

And one more caution: as a caucus with very low expected turnout, polling Nevada is at least as perilous as Iowa, if not more so.





















For the Republicans, we have only three polls taken this week. The only good news here (statistically speaking) is that McCain, Huckabee and Thompson are all tightly clustered without the large variation we saw for the Dems. Romney, on the other hand, shows a big gap between the first poll, completed BEFORE his win in Michigan and the two polls taken since then. Looks like a bump.

The lack of wild variation lets both trends come closer to the polls, but again just three polls is a ridiculously small number to base much on. I'd stay conservative with Blue here.

Ironic that where uncertainty is intrinsically great because of low turnout and the importance of organization that we also have magnified that uncertainty with so few polls. Makes it hard to be an odds-maker in Nevada.