Polls in September that showed Mr. Obama with a lead of eight or more percentage points in Ohio and elsewhere were a “fantasy,” [David Plouffe] said. The president’s margin of victory in battleground states was going to be “one, two, three, four points at most.” “In those states, if the election were held today, I’m as confident as anything I’ve been in my life, that we would win the election,” Mr. Plouffe said. “I assume tonight’s debate performance will strengthen that a little bit. I think it will provide some more excitement for Democrats and our supporters as Romney got additional enthusiasm off his debate.”
“But the structure of the race is pretty established,” he added.Nate Silver:
It continues to be noteworthy, in my view, that in slow news cycles — as in most of the spring and summer months — the polls have generally converged to show an overall advantage for Mr. Obama of about two percentage points. After his best news cycles, like after the Democratic convention, Mr. Obama pulled ahead in the polls by four to five points, while Mr. Romney remained about tied with Mr. Obama after his best series of events. But some of these effects could be artificial, as a result of nonresponse bias.If you want to know what Silver is referring to when he talks about "nonresponse bias," you can read what I wrote about that in a piece titled The Anatomy of a Bounce.
Perhaps the New York debate — viewed as a modest win for Mr. Obama by instant reaction polls — will reset the news cycle to a neutral enough point that the potential effects of nonresponse bias will be reduced...
On the other hand, it’s possible that Mr. Obama’s “win” in the debate will seem more definitive in the coming days, and that he’ll get a bigger bounce in the polls. If so, there will be some reason to be suspicious of it.
The sad truth of it is that we've all spent the last month riding a rollercoaster of highs, lows and back to highs again based on a quirk in polling that overstates the public's reaction to political events...while all along the reality is that "the structure of the race is pretty established."