Nate Silver is skeptical that Obama has a swing-state firewall:
Iowa, in particular, is a crucial state that has been thinly polled all year. (The FiveThirtyEight model, in fact, calculates that Iowa is slightly more essential to the Electoral College than Florida, despite having many fewer electoral votes.) There has been just one poll of Iowa since the debates, and while it gave Mr. Obama the lead, it was an automated poll that probably does not merit too much weight.
Our forecast model is more bearish on Mr. Obama’s chances in Iowa than those of our competitors. The FiveThirtyEight “now-cast” does have him in the lead there, but only by 0.8 percentage points; other polling Web sites, by contrast, put his edge at between 2 and 5 points. The difference is that the FiveThirtyEight methods are inferring a decline for Mr. Obama in Iowa because of the deterioration in his overall national standing.
The Dish 
