Of course, Romney has another problem that is clear from Republican primaries: working-class voters don’t like him. Santorum is killing Romney among non-college educated whites, an absolutely crucial demographic for Republicans this fall. I’m certainly not saying Santorum voters are going to choose Obama over Romney, but they could very well stay home.Uh-huh. This requires us to believe that the voters most antipathetic to Obama are going to stay home rather than pull a lever (or, increasingly, tap a touch-screen) against the Kenyan socialist enemy of America's very existence.
Santorum's Super-Tuesday speech to his supporters made scarcely-veiled references to Obama's being (1) black and (2) raised in part overseas, as an argument that only someone raised in a "real" American community can understand that community's problems. Anyone not immediately offended by that speech is not somebody who's going to miss a chance to vote against Obama, even if he has to vote for Romney to do it.
... Jon Chait agrees: "the best group of voters not to be getting are voters who are certain to support you in the fall."