Here's what the Obama campaign should do at some point -- maybe not now, but at some point, especially if the Clintons, aided by Geraldine Ferraro, keep their racist kneecapping going as crunch time comes. Especially in light of the Spitzer meltdown.
He should say, in that inimitable comic way he has when he refers to himself as Cheney's cousin -- he should say:
You know, people keep asking me if There's no basis for that.
He, or his surrogates, should just use line, in this context, at every opportunity. In a comic way.
As far as I know.
People will get it. Saturday Night Live will pick up on it. They are feeling guilty. As they should.