When Obama picked Biden, I heard this statement, "Biden didn't help Obama, and Biden didn't hurt Obama. And that's all Obama needed in 2008, a sort of break-even VP selection"
Biden absolutely helped Obama. He was picked entirely because he fit the stereotype/image of a moderate Democrat who would appeal to blue collar whites (and because of his 30 year Senate career). Basically the message of the pick was "The Black guy may be scary, but if he's running with old Scranton Joe, the ticket can't be too extreme or too inexperienced."
Obama's book shed some light on the issue, beyond the still fresh grudge, it seemed that everyone thought Bill Clinton walking around without a clear role would be a bad decision.
He also said that it was either Biden or Kaine (which HRC later picked) which makes me think that VP pick is something the candidate delegates to the DNC and they wanted some establishment man.
BTW reading the book the steady impression is that if anything Biden is\was to the left of Obama on almost all major issues.
