One problem is that the trend toward Mr. Obama in national polls has hardly been uniform. The Gallup national tracking poll has shown a very flat race. And Rasmussen Reports had a swing toward Mr. Romney in its release on Thursday, with his pulling ahead by four points in its survey. Weekly tracking polls from Public Policy Polling and YouGov have also not shown especially good numbers for Mr. Obama lately. If there had really been a shift in the race of the magnitude that the Real Clear Politics average implies — it has Mr. Obama gaining three points on Mr. Romney over roughly the past 10 days — we probably wouldn’t be seeing these contradictory data points.

Perhaps more importantly, there hasn’t really been a lot of news to drive something on the order of a three-point swing toward Mr. Obama. There have been far more momentous news events at earlier stages of the campaign, like the Supreme Court’s ruling on Mr. Obama’s health care bill, or the set of poor jobs reports in April through June, that didn’t seem to move the numbers much at all. So your default position should be one of skepticism toward the numbers having moved very much.