Yeah, he’s got to be careful. You know the McCain camp and their PR dept at places like Fox are all ready now to jump if Biden attacks and/or the moderator tries to reign in her rambling nonsense – sexist bullies, you know. The smart plan would be to make sure his answers are as to the point and calmly delivered as possible, and pretty much leave her completely alone. *Hopefully* people will see the difference without having to point it out, but then from this distance it seems stupidity is passable in US politics.
The problem may be that she seems to be okay at memorizing coached lines, snappy sound bites. Where she falls apart in these interviews is in any follow up question. She can remember the slogan, just doesn’t know what it all means. So if he gives her a kind of free reign and she’s not being challenged at all, just given extensive opportunites to spit out the slogans she remembers, he’s got to somehow guide her into deeper waters with his answers, but do it without directly challenging her. Somehow in his answer change the nature of the question or discussion, somehow lead the moderator to ask a follow up or put something out there that she simply can’t let pass. Once she's away from the coached and memorised soundbite, frankly, she's fucked.
Anyway, it’s not going to be easy for him. He can’t just go out there and pound her into the ground the way everybody hopes. He’s got to make her look stupid, but she has to go there on her own.