I commend this Noam Scheiber post from yesterday, and this one line at the end got me thinking of something:

There are really two broad swing groups: one working-class, the other affluent. In principle, you could win the general by winning one or the other, or some combination of the two.

Some combination, indeed. Political commentary sometimes proceeds as if we elect presidents via a demographic electoral college in which African-Americans are a mid-sized state like Wisconsin while white working class men and white working class women are, respectively, big states like Pennsylvania and Ohio. But of course it doesn't work that way. But of course it doesn't work that way. McCain gaining the support of 1,000 Kerry-voting Vermonters doesn't accomplish anything because he's hopelessly far behind in Vermont anyway. But persuading 1,000 Kerry-voting African-Americans does help him (assuming they don't live in Vermont) even though he'd still be hopelessly far behind.