With only an hour to go, the question on the tip of every pundit's tongue is how John McCain can "win" tonight's town-hall debate at Belmont University in Nashville, Tenn. 

A few things are clear enough. If "winning" means positioning oneself for victory on Election Day, McCain has a much harder night ahead of him than Barack Obama. Judging by the polls, Obama would win an election held today in a landslide--which means that he can afford to coast, to not make any mistakes. McCain, meanwhile, has to change the dynamic in order to catapult himself back into contention. And tonight's debate--an unfiltered encounter with 60-70 million potential voters--is one of his last opportunities to do it.

Given this rather inconvenient truth--and the nasty tenor of the past few days--many observers have assumed that McCain will come out swinging. "There should be drama aplenty, writes the New Republic's Noam Scheiber. "If anything, too much." But I suspect that it'd be a massive mistake for McCain to open a can of whupass on Obama. I've already written about why going negative in general may hurt McCain more than it helps him; suffice it to say that mudsling delivers diminishing returns when 40 percent of the electorate feels negatively about you. But more specifically, McCain would not be catering to any of tonight's three audiences--the audience in the hall, the audience watching on TV or the audience (like me) analyzing the event in the media--by baring his teeth.

As Bill Clinton proved, town-hall debates--i.e., debates in which a moderator fields questions from an audience of actual voters--are all about empathy. Pivoting from a citizen's well-intentioned question about, say, health care to a pre-scripted attack on Obama's patriotism will strike a seriously discordant note in the hall and give Obama yet another opportunity to paint McCain as "out of touch." (According to a new CNN poll, "55 percent of registered voters already say that Obama "cares more about people like [them]" than McCain, with [only] 35 percent saying McCain cares more than Obama). On television, the effect would be worse. The first McCain-Obama debate showed that TV viewers take style as seriously as substance; on points, the two combatants fought to a draw, but voters far preferred Obama's even temper to McCain peevish, condescending manner. Tonight, voters will be especially swayed by style, as the candidates casually orbit each other and interact with voters from a shared stage. Physically, McCain is already at a disadvantage; he's shorter and (thanks to war injuries) less graceful than Obama. Any grimace, any lurch, any refusal to make eye contact will only be magnified in this informal setting. An actual attack would seem far worse. Last but not least, the media is fully expecting McCain to throw punches. If he does, he won't make news. There's no element of surprise.

And that's the main reason I think McCain should hold back (and hold back ostentatiously). For the MSM, a "gracious McCain"--a McCain who invokes the ideals of honor, sacrifice and bipartisanship--represents a compelling, ready-made narrative: Mac is Back and being true to the better angels of his nature (instead of campaign guru Steve Schmidt). I'm not saying this will be true, necessarily. But given the expectations--and how dramatically and news-worthily such a performance would depart from them--I bet it's what Chris Matthews and Co. would say. Attacking would only reinforce the impression that McCain is erratic and angry--which is the reason he's losing in the first place. Why not do something that would actually enhance his reputation--and contradict the prevailing narrative--instead of damaging it?

Of course, simply being polite won't cut it. Town-hall debates are all about "moments"--the telling displays of emotion that catch on with the press and the public. Tonight, McCain needs a moment. More specifically, a moment that accentuates the positive aspects of his character. Over at TNR's The Plank, Jason Zengerle wrote earlier today about what could've been just such a moment for McCain:

In case you haven't seen it, watch this video [above] from a campaign rally McCain held yesterday in New Mexico. After McCain asks, "Who is the real Barack Obama?" someone in the crowd yells "Terrorist!" For a second there, McCain looks slightly taken aback, but then he pushes aside whatever qualms he might have and simply plunges ahead with the rest of his speech. What if McCain, instead of continuing with his speech, had stopped cold, looked the audience member in the eye, and gently but sternly rebuked him with a homily about how we're all Americans and the problem with Obama isn't that he's a bad man or a terrorist, but that he's wrong on the issues? Sure, it would have been hypocritical--it's no coincidence McCain's supporters think Obama's a terrorist when you've got Sarah Palin accusing him of palling around with one--but it would have been dramatic and mavericky as hell, too. It would have been the lead campaign story on all the networks, it would have become a YouTube sensation, and it would have burnished McCain's badly tarnished brand as an atypically honorable and different sort of politician. 

McCain, in other words, missed his opportunity. Tonight's town-hall debate is unscripted enough--just barely--to include the possibility of a similar moment. If McCain's smart, he should be crossing his fingers for a second chance--and he should be ready to run with it if it arrives. A good moment may not be enough to turn the tide for McCain. But it's better than the other options.

Thoughts? Disagreements? Amendments? Ad hominem attacks? The comments are all yours. Leave your take below; I'll be back later this evening with my post-show analysis.