“Between ‘Joe the Plumber’, ‘spread the wealth’ and ‘I’m not George Bush’, John McCain at least now seems to have a few somewhat more constructive talking points. So some of those crestfallen conservatives might have moved back into the likely voter universe. What I don’t know that McCain is doing, on the other hand, is actually persuading very many voters, and particularly not independents or registered Democrats.
“If that is the case, than McCain is likely to run into something of a wall very soon here, brought about [by] the Republicans’ substantial disadvantage in partisan identification.
“People sometimes misunderstand the nature of ‘momentum’ in presidential campaigns. If McCain was down 8 points yesterday and is down 6 points today, that does not mean that he is likely to be 4 points down tomorrow. On the contrary, polling in the general election seems essentially to be a random walk, with the minor stipulation that the polling has had some tendency to tighten slightly during the stretch run (as our model accounts for). That is, the polls are essentially as likely to move back toward Obama tomorrow as they are to continue to move toward McCain.
“McCain’s other problem is that the polls in battleground states have not really tightened at all. Obama gets good numbers today, for instance, in North Carolina, Wisconsin and Florida. Obama presently has something like a 3:1 advantage in advertising, and most of that advertising is concentrated in battleground states. As such, this may serve as a hedge against any improvements that McCain is able to make elsewhere in the country.” — Fivethirtyeight‘s Nate Silver, posted yesterday at 2:08 pm eastern.