I've tried my best to avoid the what they need/want/have to do nonsense and chatter. But since I've got a few minutes on my hands and I think it's pretty straightforward, just between you and I, here are my thoughts.

Obama's brief is really simple: make this debate just like the first two. No need for fireworks or decisive blows. Just seem reassuring, knowledgeable, presidential. If the whole event is more or less boring, that's not a problem.

I don't think McCain can do a lot on his own to help himself in this debate. What he needs to do is come up with something, maybe just luck, that knocks Obama off his stride or sticks him with a question he can't well answer. He's got to force an error from Obama. And in that sense McCain's fate isn't in his own hands.

Separate from this 'what they need to do' nonsense, McCain's got himself into a bit of a hole, quite apart the poor poll numbers. He's being telegraphing that he's going to get all Ayersy on Obama; it's hard to see how he can't lay into him since he desperately needs to shake up the direction of the race. And yet, not only do attacks like that tend to turn off voters in general (though they're often effective if done through surrogates), but a mountain of polling evidence released in the last week shows that McCain's terrorism/Ayers attacks have done McCain great damage. I'm curious to see how McCain squares that circle.