Obama has already gone through the "elitist" flap, so I'm sure he's on the watchout for that kind of thing. (A black man is elitist? Crazy times, these.)
I think McCain is more apt to say the kinds of things that are completely insane, like singing "Bomb Iran". Bush may be mentally retarded, but the things he screws up tend to be the kinds of things you'd forgive a third grader for, so it's kind of cute and endearing to most people. "Oh look, he said 'blackies' instead of 'African-Americans'!"
With McCain, it'll be, "Oh look, he said 'cotton-pickin' ni**er' instead of 'Obama'!"
That's my prediction, anyways.