Democrats doing better in richer regions?

Earlier this week Andrew Gelman suggested that it looks like Barack Obama's election had less to do with "realignment" then an overall tilt in the electorate, which just managed to "tip" a few borderline states. This is rather clear when you look at maps of the results from 2004 to 2008. But today Gelman reports data which suggests that the gains in 2008 were disproportionately in wealthier regions. This makes sense when you inspect the McCain Belt, those counties where Republicans actually did better in 2008 than they did in 2004.