I'm inclined to think that McCain's natural perceived advantage on foreign policy may be significantly diminished by the fact that he's done little if any debate prep in the last 48 hours. As a McCain supporter, that troubles me, particularly because he was already relying on his expertise to overcome his lack of dynamism behind the mic.
Typically candidates start prepping well in advance, so it's not that he'll be totally cold, but he may be less sharp on the more recent topics, particularly if they talk about the tension with Pakistan, the Russians in Venezuela other events that have happend during the last 3-4 days.
OTOH, I thought Obama did poorly in many of his debates during the primary. His affinity for speechifying can make him appear pedantic when speaking off the cuff, and his slick image doesn't always hold up when he's forced to think on his feet as opposed to delivering prepared text. He's also got a serious problem with "umms..." that I can't believe he didn't conquer in law school.
I'm going to give the slight edge to Obama going in, particularly because the debate audience is likely to be slightly or more pro-Obama and because he's more thoroughly prepped. It's a shame from Obama's perspective that the debate isn't about the economy because he could rally his troops around their perceptions of the last several days' events and beause the first debate is typically more significant than subsequent debates.
Edit: And this FiveThirtyEight analysis of the most recent state polling highlights what's riding on tonight's performance:
http://www.fivethirtyeight.com/2008/09/ ... l#commentsMcCain gets good numbers in West Virginia and Montana, two states that looked like they might just have been on the verge of being competitive. And although Obama looks as though he's slightly ahead in New Hampshire, it also looks to be polling behind his national numbers -- we project Obama to win New Hampshire by 0.7 points, but the national popular vote by 2.9 points. So if the race tightens up, Obama may no longer be able to bank on New Hampshire's 4 electoral votes.
Still, McCain has very serious problems in Virginia, and extremely serious problems in Michigan, which is starting to drift off the swing state list. And forget about the Pacific Northwest. But at this stage, the electoral math is starting to diminish in importance; McCain needs to make gains everywhere, which means he needs a clutch performance in tonight's debate.

