If I were Ken Mehlman (Bush's campaign manager), I would strongly advise Cheney to step down during the convention (for "health" reasons of course). This would open the door for a select group of VP candidates that would be Donkey Stompers. That is, the effect they would have on the election would surely wipe out any chance Kerry would have of winning regardless of whom he chooses as a running mate.
On my original list were Rice, Powell, and Giuliani. Another astute visitor suggested that I add Elizabeth Dole to that list.
Of course, I don't think Powell would accept and I'm not sure about Giuliani. But I think the two women would have a greater effect anyway.