Scenario #1: Al Gore wins an Oscar for his movie and during his acceptance speech, he announces he will run for President. He is instantly catapulted past Hilary and goes on the win the Presidential election.
Scenario #2: As the Scooter Libby trail goes on, it comes out that not only was the VP behind leaking a CIA agent's name, but the President OK'd it. Both are impeached and Nancy Pelosi becomes the 1st woman President. She picks Hilary as her VP.
Scenario #3: The VP announces he is stepping down for health reasons (or to avoid being impeached) and Bush selects Joe Libermann as his new VP. This move is his way of getting payback on the Republican Party for throwing him under the bus. Libermann losses in a landslide to Hilary and a majority of incumbent republicans are sweep out of office with him.
Although I would hate to see the last one play-out, I could live with any of these scenarios. Could you?