I tackle that question in a new post at 538. The analysis involves constructing a model of presidential approval from 1948-2008 and forecasting values for Obama. On average he is about 9 points more popular than the model would predict. Out-of-sample predictions for Obama and past presidents are here (click to enlarge):
If anyone wants to read the 538 post, which has more details, and leave me some reactions here, I’d be grateful. This analysis will hopefully be part of an initial chapter of the 2012 book, which will focus on the broader political and economic landscape leading up to the election.