Nate Silver: Obama rebound would be based on fundamentals.
"If there is reason to suspect a rebound for Mr. Obama, it is probably based more on election fundamentals than the debates themselves. Mr. Obama's approval ratings are just strong enough, and the economy has shown just enough resiliency, that he might be a narrow favorite on each basis. One function that debates can serve is to bring elections more into line with the fundamentals."
"There is no evidence, incidentally, that the second presidential debate is any less important than the first one. On average, it has moved the polls by 2.3 percentage points in one direction or another -- almost exactly the same as after the first debate, which moved them by 2.4 percentage points on average."
http://fivethirtyeight.blogs.nytimes.com/2012/10/16/no-guarantee-of-obama-rebound-in-second-debate/