Jonathan Chait makes an interesting point in assessing the electability of Mitt Romney and Rick Santorum. It is often assumed that Santorum will drive swing voters into the arms of Barack Obama. But what kind of swing voters?

In fact, there are, very roughly speaking, two kinds of swing voters. One kind is economically conservative, socially liberal swing voters. This is the kind of voter you usually read about, because it’s the kind most familiar to political reporters – affluent and college educated. But there’s a second kind of voter at least as numerous – economically populist and socially conservative. Think of disaffected blue-collar workers, downscale white men who love guns, hate welfare, oppose free trade, and want higher taxes on the rich and corporations. Romney appeals to the former, but Santorum more to the latter.

Chait goes on to point out that the coverage of Romney’s wealth could hurt his ability to win socially conservative downscale voters. When you move beyond swing voters to look at swing states, it is worth noting that Ohio, Pennsylvania, and North Carolina loom large on the list (though Virginia and Florida are states where Romney might be stronger).

The Obama campaign will likely portray Santorum as monomaniacally focused on social issues to the exclusion of all other considerations. That could work, especially if Santorum plays into their hands. It could also backfire, like the HHS mandate appears to have backfired up to this point. But the larger problem with Santorum as the nominee would be his need to throw together an organization on the fly rather than his social conservatism.