Obama could still lose this election.
McCain is an old man with a history of health problems and a traumatic period in his past that sets him up for stress-related death. If he's elected, Palin could be President in a year or two.
That's really worth worrying about.
On the other hand, Obama could be shot by some racist nutcase. But, as tragic as that would be, I have few qualms about Joe Biden's ability to step into the office.
I could easily see her leading the first annual federal book-burning on the White House lawn.