There's not an authentic bone in Kerry's boney body! that's why his movements don't match his words, that's why he adds so many words to a sentence. He "over-sells" because when you lie, you always think you need to juice it up more. The more you watch someone like Kerry, the more you spot the tell-tale signals that he's exaggerating...and it's so offensive when a grown man has to do that for self-glorification.
George Bush is so comfortable with himself, so genuine, you instinctively know he's leveling with you. That's the major difference in the two men.