This sentence is carefully parsed:
There was little in Tuesday’s results to suggest that [Obama]'s problems with working-class whites have significantly diminished.
Well there's this: Obama won only 27 percent of white voters without college degrees in Ohio; he won 29 percent in Pennsylvania, and 34 percent of them in Indiana. Krugman seems to miss the fact that Obama is still relatively unknown, especially among people without college degrees, and that he has been up against the most famous and beloved brand in recent Democratic party politics, playing as crudely and as brutally as she can. When a former Democratic president tells white voters that Obama doesn't care about "people like you," it's difficult to make headway. Oh: and he's, er. bi-racial. To have gone from 27 percent to 34 percent in a few weeks is not transformational, but it is progress. To have done so through a blizzard of racially-tinged guilt-by-association attempts to paint him as a commie alien, is not insignificant. To have made any progress while facing the wood-chipper of the Clinton-Rove axis is remarkable.
He has a long way to go. But it's May. And the force of his current coalition remains something to behold.