I don't want to make it like Obama's unpopularity in a lot of parts of the South is solely or even mainly tied to his race. I don't believe that. Not just because I don't want to paint with too broad or over-stating a brush. But there is actually some very relevant evidence to the contrary. If you go back to 1994 and 1995 you'll remember how Bill Clinton had a very similar geographical spread to his dire unpopularity. In a sense, he became kind of black in the middle years of his presidency, notwithstanding the fact that his political appeal in 1991-92 was precisely that he was a white Southerner with all the right cultural inflections. Some of us tend to forget that this is some of what Toni Morrison meant when she famously called Clinton America's 'first black president'.
All that being said though, c'mon ... A big part of the importance of Bill Clinton this year is that he can slip into parts of the country where President Obama is a political liability and give Democrats some presidential star power. Those places are predominantly in the South or to a degree even more in the border states. You simply can't explain this phenomenon without taking the President's race into serious account. The truth is that it's not either/or but additive. The layers of politics and race are reinforcing. But it's there.