Obama advisor David Axelrod is quoted in today's Washington Post article by Dan Balz and Peter Slevin:
"I think one of the things driving the national polls is that the red states are redder," said David Axelrod, one of Obama's closest advisers. "In the battleground states, the race has held pretty firm."
An interesting claim. Let's take a look at the data based on state polls, rather than national.
Among the strong Republican states, McCain has gained more than 8 points over Obama since shortly before the conventions, turning a 14 point lead into a 22.5 point margin, a huge gain.
Among the strong Democratic states, the effect of the conventions is a tiny 2 point move in McCain's direction, from an Obama lead of 12 points before to 10 points now.
But the rest of the states, rated lean or toss up, have also shown movement. These swing states had a 1.5 point Obama lead before the conventions, and that has now turned into a 3 point McCain lead, a 4.5 point shift.
So Axelrod is right that the biggest gains for McCain have come in the reddest of states, and those may influence national polling. But the evidence doesn't back his second claim, that the battleground has held firm, unless of course you mean they are still battleground states. But now battlegrounds that on balance favor McCain rather than favor Obama as they did before the conventions.
One caution: the lean and tossup states are themselves heterogeneous, so a single trend estimate such as the 4.5 McCain lead here is itself a simplification. If you wanted to focus on the six or eight states that probably hold the key to the electoral vote, you could slice this more finely.
We currently rate eight states as pure tossup: NH, VA, OH, MI, CO, NM, NV and MT. (Note the last has few polls and the latest 9/8 shows a 53-42 McCain lead. But it does fit our statistical criteria, and Montana was listed by the Obama campaign as a target state.)
When we fit the data to just these eight tossup states, we see a 3.5 point move in McCain's direction, from a 2 point Obama lead to a 1.5 point McCain lead. Only a point less shift than among all lean and tossup states.
No matter how you slice it, the battleground states have a lot of battle left in them, and campaign events are having effects across all states, though larger in some than others.