"Is Obama Toast? Handicapping the 2012 Election."

Lots of detailed analysis from Nate Silver, who sums it up like this:

With Perry having slumped in the polls, however, and Romney the more likely nominee, the odds tilt slightly toward Obama joining the list of one-termers. It is early, and almost no matter what, the election will be a losable one for Republicans. But Obama’s position is tenuous enough that it might not be a winnable one for him.