Andrew Gelman on the region and income results from the election, using a county-level analysis:

In the midwest and west, Obama outperformed Kerry in all sorts of counties. In the northeast, Obama did just a bit better than Kerry (who had that northeastern home-state advantage). In the south, Obama did almost uniformly better in rich counties, also did well in middle-income counties (although less so in Republican-leaning areas), and basically showed no improvement from Kerry in poor counties.

So, region and income are both part of the story here. As we already know from those maps of vote swing by county. These scatterplots are another way to look at it.