THE BIDEN EFFECT....I think this poll result from the Washington Post pretty much summarizes what non-obsessives think about Obama's choice of Joe Biden for vice president: they don't care. Asked if it would affect their vote, only a quarter said it would, and that quarter was split almost down the middle. There's just no effect at all.
Which is not to say that there won't be an effect eventually, of course. If Biden says something dumb, or if McCain's attack dogs are able to dream up an effective smear campaign against him, it could turn into a mistake. But like nearly any other choice Obama could have made (Hillary Clinton is the obvious exception), he starts off as a big fat null. People just don't care that much about who the vice president is.