My post breaking down state-level support for Barack Obama is cited by Jonathan Last in today’s Philadelphia Inquirer (where we had a Spinsanity column back in 2004):

None of this is to say Obama cannot win white votes, too. His victories in quite-white Iowa, Minnesota and North Dakota all prove that. But those are caucus states and states with homogeneously white populations. Obama has not been able to win consistently in (a) primary states with (b) racial makeups closer to the national average. His victories in Missouri and Connecticut are important because they show that he can win this type of primary. But regression analysis suggests race is a factor in these contests.

Here’s Duke poli-sci fellow Brendan Nyhan summing up the phenomenon: The theory is that “Obama’s race isn’t an issue in overwhelmingly white states because race isn’t salient there, whereas Obama can win in states with large black populations using a coalition built on black support. But in states with moderate black populations, race is sufficiently salient to reduce his vote totals among whites, and he can’t ride the black vote to victory in the same way as he does in more heavily black states. I’m not sure if that’s true, but the data are at least broadly consistent with the story.” Other academics and pollsters, including the indispensable Jay Cost of Real Clear politics, have noticed much the same.