Friday, March 30, 2007

Bush Approval: Five new polls, Trend at 33.6%

Five new polls have arrived. Fox (3/27-28/07) has approval at 33%, disapproval at 61%. Time (3/23-26/07) is at 33%/60%. Gallup/USAToday (3/23-25/07) is 34%/62%. Pew (3/21-25/07) has it 33%/58%. And Democracy Corps (3/20-25/07) is at 37%/58%. The Democracy Corps samples likely voters and has a consistently positive house effect for presidential approval. With these five new polls my approval trend estimate stands at 33.6%.

Based on the sensitivity analysis below, the variability in the trend estimate has remained between 33% and 35% approval over the last 20 polls, with only a slight negative trend. So far, at least, there is little evidence that the Gonzalez/prosecutor hearings are making a substantial impact on presidential approval. With further hearings, and a looming showdown over the war funding bill/veto, things could change with new developments in DC. More on that latter.

Monday, March 26, 2007

Fred Thompson in '08?

(UPDATED 3/27/07: The new USAToday/Gallup poll is now out and it finds support for Thompson at 12%. I've updated the graph above accordingly. I've not changed the text below. The Gallup result just strengthens that argument.)

The unsettled nature of the Republican presidential nomination race can be seen by the impact of talk that former Tennessee Senator Fred Thompson is considering entering the contest. There has been little polling on Thompson-- only three questions in two years-- but the latest Zogby telephone poll (3/22-26/07)l finds Thompson at 9% support, tied with former Massachusetts Governor Mitt Romney. That a non-candidate can leap to a tie for fourth place based on only a suggestion that he might run, says more about the state of Republican preferences than does former New York City Mayor Rudy Giuliani's continuing lead in the polls. While voters are willing to pick from a list of candidates, that so many will jump to Thompson shows preferences are far from settled.

Is 9% support a lot? Not in absolute terms, but compare that to the 9% Romney receives when fully committed to his campaign and after being an active candidate for many months. (I'm talking about how he has behaved, not the date of his various declarations.)

Or compare Thompson at 9% with Arizona Senator John McCain who held the support of just 13% of the Republicans in this Zogby poll. McCain held 17% in a January Zogby poll and 20% in Zogby's February poll. His support has been declining somewhat since January.

Former House Speaker Newt Gingrich was not included in the poll. Based on other polling, Gingrich has been holding a small two percentage point lead over Romney, so Thompson would appear to slightly trail Gingrich as well. In Zogby's January poll Gingrich was at 8% and at 7% in February. It is both unfortunate and puzzling that Gingrich was dropped from the latest poll, opening a window of doubt as to where his supports went when not offered the chance to support him in the survey question. Gingrich's supporters might have been more likely to jump to Thompson with Gingrich not on the list, inflating Thompson's support.

While the change in the candidate list makes a direct assessment of Thompson's support problematic, the instability of opinion among Republicans is clear in any case. While Giuliani's support has been rising recently, and he has led McCain in the vast majority of polls since 2004, there is substantial evidence that the party is open to an alternative "challenger" to emerge from the pack.

I should also note that Zogby finds 28% of Republicans unsure of their preference for the nomination, substantially more than most polls. The amount of undecided varies quite a bit across polls, making comparison of the absolute levels of support more uncertain than usual. For example, in the candidate trend plots below, Giuliani's support is estimated at around 36% and McCain's at about 22%, compared to Zogby's estimates of 27% and 13% respectively. If pushed, the undecided might be expected to pick familiar names, possibly boosting these two.

Thompson might, or might not, prove to be a formidable candidate if he officially got into the race, rather than simply encouraging speculation. But the amount of support he has picked up on such slim efforts shows that there is a great deal of room for change in the Republican contest.

The top four Republican candidates seem to generally continue recent trends-- Giuliani rising, McCain slipping and Gingrich and Romney continuing slow but steady rises. If we add Thompson to the plot below, he would overlap that latest Romney reading, with both at 9%.

It undoubtedly bears saying clearly that this is the first poll with Thompson included since his suggestion that he might run. We should never put too much confidence in a single poll, as the spread of points around the trend lines above demonstrates. The next poll may show less support or more support. Let's hope we get some new data soon so we can better assess Thompson's potential.

To see all the polling on all the presidential contenders, updated with the new Zogby data, click here. That page is updated with each new poll, and provides a handy reference point for all the latest national primary polling.

Thursday, March 22, 2007

Bush Approval: ARG at 32%, Trend at 33.4%

Approval of President Bush has slipped to an estimated 33.4%. The new estimate adds a new poll from American Research Group (ARG) taken 3/18-21/07 with approval at 32%, disapproval at 63%.

(For a full discussion of the plots and how to interpret them, see this post.)

The approval trend has fluctuated between 33.0% and 35.5% over the past 20 polls. Some of this variation is sensitive to whether the latest poll is above or below the current trend estimate. At the moment, the most recent polls have run below the trend, and that has pulled the estimate down. None of the recent polls qualifies as an outlier, so the current estimate is unlikely to be driven by a single exceptional case. However, the fluctuations in the estimate mean that we are safest saying that approval is currently in the 33%-35% range. The trend estimate's variation is considerably less than the range of polls, as the last plot below makes vividly clear. This is an example of what we can gain in precision by using estimators that combine data from many polls, rather than relying on any single poll.

Monday, March 19, 2007

Bush Approval: Two New Polls, Trend at 33.9%

New polls by Time and Newsweek released over the weekend bring the estimated approval of President Bush to 33.9%. Both polls came in well below the previous trend estimate of 34.9% resulting in a substantial shift in the estimate. Time's poll, taken 3/9-12/07 found approval at 32%, disapproval at 61%. Newsweek's was conducted 3/14-16/07 has approval at 30%, disapproval at 60%.

A fuller explanation of these graphs is available here.

The residuals for recent trend estimates remain well behaved, and the two latest polls are well within the 95% confidence region.

Estimated approval has bounced around about as much as usual, ranging between 33% and 35% for a while now.

Friday, March 16, 2007

Bush Approval: 3 new polls, trend up to 34.9%

Despite a bad week of Washington news for the administration, President Bush's approval ratings have continued to move modestly upwards over the past week. New polls from Gallup (3/11-14/07, 35% approve/61% disapprove), Zogby (3/7-9/06, 35%/65%) and Bloomberg (3/3-11/07, 38%/60%) all find approval slightly above my previous trend estimate. The result is a small increase in the approval estimate to 34.9%.

See this post for a full explanation of the graphs here.

Note that the recent Bloomberg poll is by Bloomberg alone, not jointly with their usual polling partner, the Los Angeles Times.

None of the residuals is particularly noteworthy. The low Zogby poll is a previous result, not the most recent which is very close to the trend estimate (and overprinted as a result.)

The variability of the approval estimate remains within the range of recent estimates.

Tuesday, March 13, 2007

Is Bush the New Truman?

One of the most frequent searches of PoliticalArithmetik is some variation on how low can approval of President Bush go. President Truman holds the all time low record, at 22%, and the comparison of Bush to Truman comes up a lot. So let's take a look at second term presidents who had generally low approval ratings. (That leaves out Eisenhower, Reagan and Clinton, plus the ones who never got a second term.)

It turns out the Bush-Truman comparison is a pretty good one in terms of both trends and levels of approval. Truman's bounces are similar to those of Bush and the current level of approval and its trend are quite close. In comparison, Johnson did better throughout his war, while Nixon sank lower and quicker as Watergate came to dominate public perceptions.

This doesn't mean that Bush will necessarily challenge Truman's lows, however. Throughout his presidency, Bush has maintained a considerably greater loyalty among Republicans than Truman did among Democrats. I wrote about this earlier here. At his low point, Truman was supported by less than half of all Democrats. Bush has never fallen below 70% approval among Republicans in Gallup polls. (He has been lower in other organization's polling, though not by a lot.) His support among Republicans in Gallup polls taken since January 1, 2007 are in order 79, 71, 76, 78, 76, and 70, for an average of 75.0%. By comparison, in the same period of 2005 Republican approval was consistently in the low 90s, averaging 91.1%. For the same period in 2006 it was mostly in the 80s, averaging 82.1%. So while Republican support has eroded significantly in the last two years, it remains well above Truman's lows among Democrats.

I don't think current trends alone are good predictors of future approval. Circumstances, events and presidential behavior drive approval, not a blind trend. So things could move up or down depending. But that said the comparison of Bush and Truman's approval trajectories is striking.

(Thanks to Phil Klinkner for provoking me to look at this.)

P.S. Some argue that being the "new Truman" is a good thing-- that history will judge President Bush much more favorably than do his contemporaries, just as has happened with Truman. I have no view on this aspect of Bush as the New Truman. I'm only concerned with the approval ratings here.

Monday, March 12, 2007

Bush Approval: 4 New Polls, Trend up to 34.7%

Four new polls have come in since Friday, lifting President Bush's approval trend estimate to 34.7%, from last week's 33.4%. The new polls are AP/Ipsos (3/5-7/07, 35% Approve/65% Disapprove), CBS/New York Times (3/7-11/07, 34%/58%), CNN/ORC (3/9-11/07, 37%/57%) and LATimes/Bloomberg (3/3-11/07, 38% Approval, the disapprove rate has not yet been released.) With four polls all coming in above the previous trend estimate, the evidence favors an increased approval rate over last week. However, there remains quite a bit of noise in the estimates.

The new CBS polls shows approval of President Bush from Republicans rising substantially since January, when it was 63% to 65% in February and 75% in the latest poll. One advantage of a Democratic Congress for the President is it gives his partisans an opponent to blame, and may as a result help improve the President's support among Republicans. We'll have to look into this a bit more systematically.

For a full description of these graphs, please see this earlier post.

The last six polls appear below.

With the new estimate of approval, all four new polls (and indeed, all of the last six) are pretty close to the estimated trend. This at least means that no single outlier is unduly influencing the current estimate.

The residuals, deviations around the trend, are shown below. (Note that the CBS/NYT poll that appears outside the lower 95% confidence limit is an older poll from 2/23-27/07, not the latest one. That one has been inside the confidence interval until recent polling revised the trend up a bit. This kind of dynamic is common until more than a dozen or so polls are available after any single date.)

To assess the variability of the trend estimator, I run 20,000 bootstrap samples of the approval series, and estimate the trend 20,000 times. The gray region below shows all these samples, while the blue line is the current estimate.

It is worth noticing that the spread of estimates over the past two or three months has been a bit wider than earlier parts of the series. In part this reflects an intrinsically greater uncertainty of the estimate at the end of the series. However, it also seems that the approval polling since the November election has also been a bit more variable than in most of 2005-06. Whether this reflects a plateau in approval with more randomness around a roughly stable mean, or if the shift to a Democratic congress has allowed for more variability is an interesting question.

Finally, we can take out each of the last 20 estimates and see how sensitive the trend has been to these polls.

There has been quite a bit of variability, foretold by the bootstrap results, over a range of about 5 points for the trend estimator. That's a lot less than the range of polls, as you can see dramatically in the figure but still shows that the trend estimate is itself subject to uncertainty.

Friday, March 09, 2007

Giuliani Leads; Press finally notices

Since November 2004, former New York Mayor Rudy Giuliani has consistently led Arizona Senator John McCain for the Republican presidential nomination. Giuliani has led in 46 of 57 national polls since then, with 5 more polls tied. McCain has led in only 10.5% of all polls. In the last two months, the size of that lead has increased substantially.

Despite this consistent polling result, newspaper stories have overwhelmingly referred to McCain as the "front runner", while seldom saying the same about Giuliani. Since May 1, 2005, 555 articles in Lexis/Nexis's database of US News have mentioned "front runner" and McCain, Giuliani or both in the same sentence. In 65% of these article, McCain is connected to front runner, while Giuliani's name has not appeared. Only 10% of articles mentioned Giuliani but not McCain, while 25% of articles mentioned both. (I made this point in a December post, here, before the current surge in Giuliani support.)

Only in the last month (and especially the first week of March, when these data end) have reporters responded to the polling data, but in a somewhat misleading form. A number of reports have framed the increased support for Giuliani as a surge from behind, when in fact he was leading all along, albeit by a small margin. Yet that small margin was quite consistent if reporters had bothered to look at the data.

A clear reason for this emphasis on McCain has been Giuliani's slow start on staff and campaigning. In addition reporter's (and informed observers') view that Giuliani's social issue positions represented a large barrier to obtaining the nomination, has led many to discount the import of the polling lead in characterizing the race. And indeed, these may ultimately doom his campaign. But that isn't what the data say now, or have been saying for over two years.

But the recent polls should serve as a warning that sometimes you should pay attention to the data. The apparent surprise at Giuliani's recent lead, expressed in many articles, should not be so surprising at all if the data were taken seriously.

I am not making an argument that Giuliani's lead now is a prediction of the future. I AM saying that to understand political dynamics you must look at them in the context of all the evidence, in this case all the polling data. Reporters would produce better informed stories if they did so.

Thursday, March 08, 2007

Bush Approval: NBC/WSJ 35%, Trend at 33.4%

The new NBC/Wall Street Journal poll, taken 3/2-5/07, finds approval of President Bush at 35% and disapproval at 60%. Those results are identical to the previous NBC/WSJ poll taken 1/17-20/07. With the new poll my estimate of approval (the blue line) now stands at 33.4%.

For a detailed explanation of the graphs here, see this post. The goal of these plots is to place each poll in the context of the estimated trend, other polls, deviations from the trend, and the variability of these estimates over time.

The most recent six polls are shown below, along with the trend estimate. To see the entire set of 19 recent polls visit the approval page at here.

The deviations from the trend give a sense of when polls are within the expected range of values we would expect due to random sampling and non-sampling errors. The 95% confidence interval plotted here shows the region within which 95% of polls fall. Polls outside that range are "outliers" and should be viewed as unexpectedly far from trend. There are various reasons why a poll might fall outside this range, and a single outlier should not be considered evidence of "bad" polling. But such polls should be interpreted skeptically in terms of where approval actually stands. The trend estimate remains the best estimate of approval at any point in time.

The trend estimator itself is subject to variability due to the timing of polls by various organizations. The plot below shows the range of estimated trends based on 20,000 bootstrap replications of the trend estimator. This is a conservative estimate of how variable the trend estimator is.

Each new poll at the end of the time series exerts significant influence on the latest estimated trend. This estimate will vary as new polls come in. The plot below shows the estimates for the last 20 "latest polls." The blue trend line is our best estimator of the path of approval after looking over all the available data. The variation in the red dots shows how much this has varied over the past 20 polls.

Tuesday, March 06, 2007

Bush Approval: 33.1% and A New Look

Public approval of President Bush's handling of his job has fallen to 33.1% after a weekend of new polling. Polls from Newsweek (2/28-3/1/07, 31% Approval, 61% Disapproval), Zogby (3/1-2/07, 30%/69%) and Gallup (3/2-4/07, 33%/63%) have pulled approval down from a high estimate last week of 35.5%.

This post also introduces a new look at the approval estimates. The central theme of my analysis of presidential approval has been to present the results "in context". The worst failing of reporting common to polling stories is the exaggeration of results based on single polls without regard to other nearly simultaneous results. Some reports emphasize the CBS/New York Times Poll taken 2/23-27 at 29%, while others stress the ABC/Washington Post poll of 2/22-25 at 36%. The former represents "a new low" while the latter is an "upturn". Yet both are within the range of results we would expect if approval is "really" around 33% (as I predicted here.) The myopic focus on individual polls undermines the credibility of probability sample polling by ignoring the variability that sampling theory predicts.

By looking at polls in context with other polls and over time, I aim to temper our interpretations by focusing on the common trend in approval polls, rather than emphasizing extreme results (in either direction.)

The trend estimate, plotted in blue in the figure above, is a local regression fit to the approval series. The advantage of local regression is that it can flexibly fit data with lots of "bumps and wiggles". The local regression will run through the "middle" of the data, with roughly equal numbers of polls above and below the trend line.

To see the most recent polls in context, I'm going to start posting the graph below-- a plot of the six latest polls showing the blue trend estimate and the data for each of the six polls.

This plot allows easy comparison of each poll with the trend, revealing polls that tend to run above or below the trend, an example of "house effects" which reflect persistent differences among polling organizations. These difference can be due to question wording, the size of "don't know" responses, sampling frames (adults versus likely voters, for example), question order and a variety of other causes. The plots above make clear both the size of such effects and the tendency of all quality polls to move up and down with the trend line regardless of house effects. In the plot above, Fox tends to produce results a bit above the trend, while CBS/NYT tend to be a bit below the trend line. But both polls move up and down with the trend, demonstrating that they are responding to the same changes in approval, even if the house effects produce persistent shifts from the trend.

This "six poll plot" also makes it clear how much variation there has been over recent polling so whatever the latest poll is, it can be seen in relation to both the trend estimate and to five other polls and past results of the same poll. If a poll is "out of line" with others, the six poll plot will make that immediately clear.

The next question about polls is whether they remain mostly within a reasonable interval of the trend estimate. When a poll falls beyond the range we expect due to random sampling plus non-sampling errors, it should be clear that the result is "unusual". This could be due to a sudden change in approval, but is more often just a random fluke, in which case the next poll by that organization usually returns to the range of other polling.

This reasonable interval is taken here to be a 95% confidence interval. I've estimated this for the 2005-present polling. Using all polls since 2002 produces little difference. The impact of 9/11 makes the 2001 data more variable than more recent years so I exclude that year in calculations of variability. The estimate I use includes the effects of non-sampling errors as well as sampling. The typical poll here has a sampling error of about +/- 3.0% to +/-3.5%. The actual 95% confidence interval is around +/- 5%. That increase from around 3% to around 5% reflects house effects, question wording, and everything else that increases poll variability beyond what is due to sampling alone. This is a more realistic estimate of the variability of poll results.

Plotting the residuals (the observed approval minus that predicted by the trend line) over time makes clear how variable polls are, and indicates which ones fall outside the 95% confidence interval. Here I highlight and label the last 10 polls to provide context. The plot below shows this view of current polling.

When a poll falls outside of this interval, it is further away from the trend estimate than we would expect 95% of the time. However, this doesn't mean the poll is "bad" and especially doesn't mean the survey organization is of poor quality. By definition, 5% of polls will fall outside this interval, so condemning polls or pollsters that occasionally produce these "outliers" is a bit harsh. We might wish to discount such polls, until supported by more evidence, or we might worry if we see a persistent pattern of outliers from an organization. But an occasional outlier is inevitable. This plot lets us spot such outliers immediately.

The plot also lets us see the variability in the last ten polls relative to the trend estimate. This is another way to see results in context. In the current plot, it is clear that while four polls have fallen well below the trend, there have been three of the last 10 polls that are equally far above the trend estimate. This range of +/- 5 points puts the extreme polls in context of all the variability we have seen recently.

Just as it is important to look at variability across polls, it is also important to examine the variability in the trend estimate. My local regression estimate has some advantages over simple rolling averages, but it is not without its own uncertainties. For example, it takes some 10-12 polls before changes in trend have been clearly identified by the estimator. Which polls happen to be "latest" at any moment have significant influence on the estimate. For example CBS/NYT at 29% pulled the estimate down when that was the latest, while the ABC/WP at 36% pulled the estimate up. This means that the current estimate can vary depending on which polls happen to be the latest. There is also uncertainty in the trend due to which polls are observed and when they are taken. To get a look at this uncertainty in the estimate, I create a "bootstrap" estimate of 20,000 replications of the approval series. Each of these bootstrap samples draws a random selection of all the polls, but allows a poll to be selected more than once or to not be selected at all. Each poll is equally likely to be sampled. For each sample, the full trend is estimated. In the end we see 20,000 estimates of the trend which vary due to the random draws of polls to include. This gives a good estimate of the variability the blue trend estimate might have if a different set of polls had been observed.

The result of this bootstrap estimation is presented below. The gray area is the full range of 20,000 samples, while the blue line is the estimate based on the actual polls we have.

The range of estimates is generally fairly close to the trend estimate, and certainly much closer than the range of actual polls around the trend. But it is also clear that the variability at the end of the series is a bit larger than it is in the interior of the series. This reflects the influence of late observations. This influence is reduced when there are polls on both sides to stabilize the trend estimate.

Finally, the estimate of the "current" approval level, varies up and down with each new poll. To see how sensitive this estimate is, I add a new plot below. It plots the "current" estimate when each of the last 20 polls was the latest. The variability of these around the blue line shows how much uncertainty we should have about the current estimate. The blue line is always our current best estimate of the trend (and the current approval.) But new data will change that a bit. The red points below remind us how much the estimate has varied recently.

All polls are subject to random variability. By looking at polls in context--- compared to the recent past, to other polls and to themselves over time--- we can gain a clear understanding of the state of presidential approval and its dynamics over the course of an administration. The graphs above provide a consistent and systematic look at the context of polling and the variability of the trend estimate which is our best estimate of where approval stands at any moment.

Monday, March 05, 2007

National Journal 2006 Liberal/Conservative Scores

All these graphs plus large format poster-size extras are available in high resolution .pdf format here.

National Journal released their 2006 liberal-conservative roll call scores for the House and Senate last week. The National Journal report of these scores is here. National Journal's scores are interesting because they calculate separate scores for economic, social and foreign policy dimensions, plus overall scores. They also use more roll calls in each issue area than most interest groups use in their "support scores". NJ uses 30-40 roll calls each for economic and social, and 17 or 18 votes for foreign policy. That compares to as few as 10 in the typical interest group rating.

By all means go to National Journal's site for the scores of individual members and for NJ's write reports on these results. They make it easy to find individuals or to look at the entire range of scores. Plus the reporting by Richard Cohen here is a good read.

I've used "Conservatism" score here. The NJ's liberalism score is 100-Conservatism, so the scores are mirror images of each other. (This is not exactly true of the three components, but they are near-mirrors so I only use the conservative score there as well.) Using this measure makes ideology score run left-to-right as it should for the graphs.

There are 44 Democratic Senators rated for 2006. Jay Rockefeller (WV) missed more than half the votes on social issues and was therefore excluded by National Journal from the overall rating (his conservatism scores were 37 and 39 on economic and foreign issues, which would put him near Blanche Lincoln (AR), who is the 5th most conservative Democrat.)

Members of the 109th Congress who did not return to the 110th are marked with an asterisk (*).

The top two plots show the Senate parties. The location of presidential hopefuls will be of interest, as will that of Joe Lieberman (9th most conservative among Dems) followed by a not-so-distant Hillary Clinton at 13th most conservative (32nd most liberal), only 4 spots to the left of Lieberman. By contrast Barack Obama ranks as the 10th most liberal Democrat (35th most conservative). The other two current Senators are Chris Dodd (CT) at 17th most liberal (28th most conservative) and Joe Biden (DE) at 24th most liberal (21st most conservative).

On the Republican side, John McCain (AZ) earns his moderate image by scoring as the 46th most conservative of 55 Republicans. Sam Brownback (KS) is 35th and Chuck Hagel (NE) is 29th.

If we look at the three subscales National Journal uses we find a couple of interesting things.

First, the three subscales are a bit more consistent with each other for Democrats than for Republicans. The red-Republican points the the three top left plots show relatively little relationship. The Democrats also show more scatter for the Foreign-Social relationship. This could be because the areas are not as ideologically integrated for Republicans as for Democrats, or it could be that the scaling is not that stable, even with 30 something votes. (Political scientists tend to use ALL non-unanimous roll calls for such scaling efforts, rather than just a few dozen. Those efforts have consistently found that roll calls fit a single dimension quite well, and do not require separate dimensions for social, economic or foreign policy domains. If that is right, then we might expect MORE relationship between these subscales than we see. Perhaps we'll get a look at this issue in some future analysis.)

It is interesting to note Sen. Joe Lieberman's positions in the plot above. The plots show quite well that Lieberman is unusual only on the foreign dimension, where his voting record makes him the most conservative Democrat (but among the 5 most liberal Republicans on the foreign policy domain.) On economic and social issues, he appears well within the range of Democratic senators and quite clearly to the left of all Republicans. This has serious implications for talk of a possible party switch. Unless his voting behavior changed, he would be the most liberal Republican by a fair margin.

For all the talk of bipartisanship, there is little ideological overlap of Senators.

Ben Nelson (NE) is by far the most conservative Democrat. But take him out (and with the defeat of Lincoln Chafee (RI) ) and there is literally no overlap between the parties' Senators. While the least conservative Republicans (Snowe, Collins, Specter, Coleman and Smith) have shown some willingness to vote with Democrats, and the most conservative Democrats (Nelson, Landrieu, Pryor, Nelson (FL)) sometimes cross party lines, there is less basis for ideological agreement than there was in the past when more members ideologies overlapped their party affiliations. Not that anyone really expects bipartisanship to break out anytime soon.

One other interesting result in the Senate plot is the line of "perfect" social conservative scores in the plot of the subscales above. Eighteen Republican Senators took the conservative position on social issues on every vote. But in the plot you can also see that this group varies quite a bit on the economic and foreign dimensions. While this group certainly defines the most conservative end of the Republican party, there is still a fair bit of variation in their overall conservatism scores, as seen below.

On the House side, with many more members, there is also a bit more partisan overlap, though less sign of bipartisanship.

The coherence of votes across policy domains (below) look about the same for the House as for the Senate. Again the Democrats appear somewhat more correlated across domains than do Republicans. Given the image of Republican unity in the House in the 109th Congress this remains a bit of a puzzle.

The entire House is plotted by party in the high resolution .pdf file here There are multiple plots for letter size paper plus oversized posters for all members of each party.