McCain’s Mission? Impossible.

Wednesday’s debate may be his last chance to win this race.

Setting up for the final debate in Hempstead, N.Y.

To get a sense of what John McCain is going through on the eve of the last presidential debate with 20 days before Election Day and Barack Obama leading in the polls, I decided to put some pressure on myself: I delayed working on this story until 45 minutes before my deadline. To approximate the string of people in McCain’s ear offering advice, I turned on Fox News and Rush Limbaugh. Be the happy warrior! Attack! Talk about Ayers! Don’t mention Ayers! Fire your campaign staff! ACORN! I then put Wagner on my iTunes.

I’m finding it very hard to concentrate. If we’re all lucky, I may just give up and end this piece right here.

OK, maybe not.

I’m sure McCain finds it hard to concentrate, too. He is tough and likes challenging situations. But for McCain, Wednesday’s debate comes with a degree of difficulty perhaps beyond the capacity of human achievement. That sounds like the obligatory hyperbole required to create false drama for the debate (so that we might justify our hyperbole after the debate is over). But after doing the tabulations, this is where I come down.

Wednesday night is McCain’s last big chance to reach a wide national audience without the media filter. Obama is ahead in the national and state polls. By Pollster.com’s tabulation, Obama is comfortably ahead in states that would give him 256 electoral votes. By that measure, he needs only 14 more electoral votes to win. Obama is ahead in polls in states like Wisconsin, Minnesota, and New Mexico, which could give him that magic number. And the picture looks no better nationally: As John Harwood of the New York Times noted recently, only Ronald Reagan in 1980 came back from the deficit McCain faces. This isn’t to say that McCain can’t come back. It’s just that the weather looks really bad for him.

After the debate, there will be only 19 days left to campaign. After about Oct. 21st—13 days before Election Day—there will be more states to go to than there will be days left to go to them. Without a big debate moment, McCain might be able to dismantle his opponent through advertisements, local media, visits to battleground states, and luck in the news cycle. But that would require a level of precise execution his campaign has not yet shown. Given that unlikelihood, the debate is a big opportunity.

Of course, McCain could just present himself as a nice guy and hope for the best. Sure, there are ways he could win, but they are increasingly fantastical—and they are all out of McCain’s hands: All those new Democrats that have been registering in battleground states could stay home on Election Day. There could be a news development, like the discovery of Bush’s DUI charge late in 2000 or the Osama Bin Laden tape that surfaced late in 2004, that knocks the race on its ear. A huge bout of buyer’s remorse could kick in after it appears that Obama has the race locked up.

If McCain wants to take his destiny into his own hands, he has to knock Obama back. The problem for McCain is that pulling off an effective attack in a debate is like making a soufflé in a highway median. (The honking alone makes it very difficult.) It’s hard to be aggressive in a debate because the format is so regulated and the risk of coming off as a brute is so high.

And, historically, the candidate who goes negative in a debate almost always comes off poorly. Bob Dole may have secured Gerald Ford’s defeat when, in the 1976 vice-presidential debate, he got nasty and blamed Democrats for a string of wars. Jimmy Carter looked cold and snippy in 1980 next to Ronald Reagan. Lloyd Bentsen was the only candidate who successfully got off an attack line with his crack about his friend Jack Kennedy in his 1988 vice-presidential debate against Dan Quayle.

Even if McCain could overcome history and avoid Obama’s effort to portray him as intemperate and erratic, he also has to overcome his recent ineffectiveness. According to the most recent Washington Post/ABC poll, as McCain has increased his attacks on Obama, two poll numbers have also increased: McCain’s negatives and Obama’s positives. Voters now give Obama the edge on leadership for the first time in the election, and they consider McCain the riskier choice.

Obama is hardly invincible. He has dodged questions, for example, by giving unrealistic answers about how his priorities would shift given the current economic crisis. He has also been less than candid about his thinking on Iraq in light of developments in the last few months. He has overstated his abilities as a bipartisan deal-maker and truth-teller. (And his campaign isn’t terribly transparent.) It’s hard to see, though, how McCain could take advantage of these issues in a way that changes the dynamic of the race.

McCain’s other challenge is that Obama is not his only target. He’s got to do something to improve his lot with voters who care about the economy. Despite “suspending his campaign” to assist in forming a financial rescue package (or perhaps because of it), McCain continues to trail his opponent badly when voters are asked to evaluate the candidates on the economy.

As the two candidates head into the debate, both have unveiled new programs aimed at helping regular Americans in a financial pinch. McCain has also offered a new pitch about character: He’s a fighter. The message is actually a cleaner version of his acceptance speech. (Perhaps the editors were barred from the room this time.) It’s also the message Hillary Clinton offered at the end of her campaign—but Clinton was far more effective in explaining how she was going to fight on behalf of the middle class.

McCain never really explains why his ability to fight, to buck his party, or to do unpopular things is going to improve anyone’s life. Yes, he’s been tested more, and endured more in life, than Barack Obama. But voters want to know: How’s that help me? McCain has got one more night to make the case.