Jon Chait points to a recent Gallup poll which finds that Obama's lead over Clinton among white, college-educated Democrats has risen five points in the past three weeks, and among those with post-graduate degrees it has jumped from an 8-point lead to a 29-point lead. Meanwhile, he's still down 30 percent among white voters with a high school degree or less. And I have to admit, though there has been discussion about this for a year now, like Chait I was initially less concerned about this than I am now, and figured exposure and information would cut it down considerable. But it is somewhat troublesome in it's persistence as we head toward the general election.

It's not like Obama isn't trying with these voters. His campaign in Pennsylvania has been all about them, as I attempted to document when I was following him last week. But it's a very uphill battle, and I have to worry that there are insurmountable race and class issues that might never convince a number of these folks to vote for him, no matter how hard he tries to repackage his message. That said, there's a considerable slice of the electorate would never vote for Clinton, no matter what she says or does.

--Kate Sheppard