I'm actually thinking that McCain might "win" this one. He's not going to be grumpy and erratic. He's not going to attack Obama, bring up Ayers or Wright, or any number of things which, in the end, will play into Obama's hands.
He has to talk about the economy. He has to give his plans for economic turnaround. He has to distance himself from the economic policies of the past. Can he do it?
Well, if he gives the same answers he's been giving in the past, no. But his advisors know this by now, so he's got to have something new. Not necessarily a new policy, but a new way of phrasing his policy.
Of course, the subjects will be broad, and McCain is pretty good at these town hall things. If he is "happy McCain", and I think he will be, that might be enough to pull an upset. More than ever, Obama has to be warm, but remain serious.