Any criticism or disagreement with Obama will be casually dismissed as underhanded and racist. Heaven help us if he doesn't win. It will be characterized as evidence that Jim Crow is alive and well in John McCain's America.
The only reason the liberal (though likeable) Obama is a serious democrat candidate is because he is black. It’s certainly not because of his accomplishments.
If he is defeated along the way, racism won’t be the reason that many people vote for someone else... or don’t vote at all.