"One big thing to consider when mulling over possible VP selections for either party is this: If the candidate is a sitting congressman and is elected VP, who's going to replace him? With razor thin Democratic majorities in both houses, neither party is going to want a VP candidate whose seat might be given to the other party by gubernatorial appointment or special election. For example, there's absolutely no possibility that Obama is going to select Bill Nelson of Florida, because Florida's Republican governor, Charlie Crist, would get to appoint a replacement for at least the next two years of Nelson's term. That Joe Biden isn't afflicted by a similar problem (Delaware's governor is a Democrat) is a point in his favor.'

Two things:

1. The Democrat majority will not be slim after this election. Estimates of 60% Democrat majorities in both houses are not uncommon nor unrealistic.

2. The VP is still president of the Senate and votes to bread ties there.