He's a bet that will get no takers:
Suppose W's tumble was caused by bumping into a Secret Service agent. I'd wager W's first words would be "You OK son?"
If questioned by the press about the fall W would laugh it off.
According to this story about Bush's fall, he actually posed and gave photographers a chance to take pitures of his abrasions.
That would make a GREAT them/us political cartoon. One side shows Kerry flat on his face in the snow yelling "You clumsy ^&%#@(*" at the SS guy. The other shows Bush flat on his face on the trail asking your question.