it is likely that Biden will come out behind; not because of anything he does or doesn't do but simply because he's up against a woman and because the expectation games.
And before any resident feminists (or Republicans in feminist clothing) chide me for saying its different because Biden is facing a woman, all the evidence points to this being the case. Barak lost voters in the primary season when he was snarky and confrontational with Clinton and we've already seen Republicans go to the "Thats sexist" card. Biden must NOT appear to be condescending in anyway.