ST. LOUIS — Donald Trump has nothing to lose. But what does he have to gain?

Never in the modern era has any candidate entered a consequential debate in such a degraded position: Trump isn’t merely facing an uphill climb (as John McCain did in 2008) or the widespread perception he’s not up to the job (Gerald Ford in 1976) or even that he was too unlikeable to get elected (Richard Nixon in 1960). No, he’s having to grapple with all of these problems at once while cloaked in disgrace and coping with an unprecedented defection of more than two dozen Republican former supporters who feel that endorsing him has become a moral transgression.


And still, even as senior Republican leaders muse about the possibility of replacing the third-party-type invader who took over their floundering party, hints of what might have been: He's down just 4 percentage points in many national polls.

And Sunday saw the last round of polls taken before the release of Trump’s gross and grossly offensive 2005 sex-talk tape. They weren’t great for him — CBS had him down by 4 points in Ohio and Wisconsin — but those would have been surmountable deficits had he not faced his Friday catastrophe.

Things might change, but the “Trump could still turn it around” caveat is now nothing but yadda-yadda-yadda: Even an exceptional performance at the debate here tonight might not be enough to make a big difference. But, hey, this is Donald Trump, so it’s going to be must-see-TV.

Here are five things to watch.

How will real humans react to Donald Trump? Anderson Cooper and Martha Raddatz, two seasoned moderators of the don’t-suffer-fools variety, will drive Sunday’s conversation, but the 90-minute showdown at Washington University will feature a (relatively) freewheeling town hall format that often leads to wild-card moments. Politicians find it harder to weasel out of tough questions when they are hurled at them by a single mother working three jobs than a millionaire anchor with houses on each coast.

Prior to Friday, there was some question whether Clinton (who is at her best when interacting with regular people, listening to their questions like a caseworker collecting a client’s information) or Trump (a master showman with a funny, irreverent style) enjoyed an advantage.

That seems like ages ago. The real action won’t be on the stage, but in the audience of undecided voters who will question the candidates: What will they ask Trump about the revelation that he admitted to groping women and treated them like playthings to be bought with a boob job or bedroom set. And how will they react to his answers?

This is one debate where an audience reaction shot might be the most memorable moment of the night.

Play this game at home: What would you say if you were Trump? That’s a question many of the estimated 70 million viewers will ask themselves — and if nobody can answer it, he’s basically cooked.

Hillary Clinton would be in major trouble if Trump weren’t imploding. Clinton, an Edsel candidate with a Maserati operation, has been blessed by unbelievably good fortune in drawing Trump as an opponent in the first place. He is, arguably, the only potential opponent whose unpopularity outpaces her own. That was never more apparent than on Friday, when WikiLeaks (presumably in cahoots with Russian intelligence) released a bombshell trove of damaging emails from the hacked Gmail account of Clinton campaign chairman John Podesta that would, in normal times, be the only topic of pre-debate analysis.

Good thing for her that Julian Assange and the Kremlin are so ignorant of American presidential politics: Here was an “October surprise” that would have been a far more devastating “May surprise.” The crown jewels, first discovered by Buzzfeed’s Ruby Cramer, was a summary of Clinton’s infamous Wall Street speech transcripts, flagged for the nastiest bits by a member of the campaign research staff.

Let’s start with the fact that she basically confirmed all of Bernie Sanders’ worst suspicions about her innermost opinions about free trade and Wall Street — telling some of the world’s fattest-cat bankers that they, and not those raggedy reformers, should play a central role in self-regulation and the government’s response to the 2008 global financial crisis.

In another speech, she went all One World, telling another $2,000-suit crowd that her “dream is a hemispheric common market, with open trade and open borders, some time in the future with energy that is as green and sustainable as we can get it, powering growth and opportunity for every person in the hemisphere.”

Donald Trump will surely slam her on the “open borders” crack, which contradicts Clinton’s public statements that she’s in favor of closed, carefully policed borders.

But it was the expression of her wink-wink governing strategy that seems to be the most damaging revelation of all, a somewhat nuanced admission that she believes in keeping two sets of political books, one for the powerful insiders who really run things, another for the overly excitable under-informed hoi polloi who just don’t understand that the ruling class has everything figured out, more or less.

"I mean, politics is like sausage being made,” she said. “It is unsavory, and it always has been that way, but we usually end up where we need to be. But if everybody’s watching, you know, all of the back room discussions and the deals, you know, then people get a little nervous, to say the least. So, you need both a public and a private position.”

Trump can’t really say anything to make it better. But he’s got to try. His poorly lit, robotically recited and defiantly half-assed videotaped apology released under pressure from his staff late Friday was laughably (or cry-ably) inadequate. There’s a good reason that so few surrogates (apart from the let-no-cable-slot-go-unfilled defender Rudy Giuliani, who suggested Trump will ask for “forgiveness”) are jumping to his defense. It’s indefensible. Mike Pence, the discreet Indiana governor who has proved his political savvy over the past week, has scrubbed his schedule, avoiding Trump’s scandal as if it were a dying squirrel on the doorstep. Eventually Pence will have to deal with it, but let’s see if the thing can crawl away on its own.

Trump’s unavoidable-for-comment campaign manager, the disciplined pollster Kellyanne Conway (who co-authored a book with a Democratic pollster on the increasing power of women in U.S. elections), has also temporarily entered the talking-head witness protection program; the candidate’s omnipresent defenders — his kids — have been nowhere. Even his ally Ben Carson (whom Trump has privately demeaned as “an idiot”) saw fit to express his deep disgust at Trump before reaffirming his fealty.

Which is to say, the only person who can limit the damage is the candidate himself, and that’s why that the rumor he would skip the debate persisted well into the weekend despite his campaign’s denials. Several Republicans, including two who still talk to Trump, told me that they thought nothing short of a bended-knee expression of contrition would do, an admission that he’s had a problem with women, and that he’s a better man now than he was in 2005. There’s no indication Trump will actually do that — it would be wildly out of character — and even a tearful apology probably wouldn’t do it, although it would make for one of the most riveting reality-TV moments of all time.

He can, of course, temper the torment. And he’s likely to do his standard three-step, previewed on his video and in subsequent dial-in chats with favored reporters. 1) He’ll offer a broad, scripted mea culpa. 2) He’ll take a page (ironically) from Bill Clinton’s 1992 strategy in coping with the Gennifer Flowers firestorm by dodging questions and talking about “the country.” 3) He’ll go on the attack, likely a sustained assault on damaging details from her campaign’s hacked email trove and a more sustained examination of the Clinton Foundation.

All of these tactics are intelligent primary campaign politics, and Trump, as always, is doing a good job at nailing down his core support (one post-tape poll showed the overwhelming majority of Republicans sticking with him). But, even during the best of times, Trump has done a pathetic job at expanding his base. The good news from the POLITICO/Morning Consult poll take after Friday’s meltdown is that Clinton ticked up to just 42 percent, a 1-point gain. The bad news? He’s stuck at 36 percent — below the bottom end of an iron-bound 38 percent to 43 percent range he’s maintained in national polls all year.

Voters were already tuning out before Friday, and it’s hard to imagine they would be more persuadable after his private utterances were made public.

Will Trump go after Bill Clinton? The Clinton campaign is spinning the idea that they believe Trump will use the town hall to rehash the former president’s affairs — and the years-old allegation (unproven and unprosecuted) that he raped a woman in the 1970s. In part, that’s because it might happen, but mostly it’s because they really, really want him to.

Trump, as he has done repeatedly, hinted at a scorched-earth debate strategy. On Saturday he retweeted Clinton accuser Juanita Broaddrick mocking Hillary Clinton’s statement that Trump’s statements about women were “horrific.” The Democratic nominee, she wrote, “lives with and protects a ‘Rapist,’” she wrote. After his own tape came out, he quipped that Bill Clinton had said much worse during rounds of golf.

If he does that, it would be one of the dumbest moves he’s ever made, an invitation to a longer discussion of the many other instances of boorishness and misogynistic statements in his past. Never mind the context: The town hall is supposed to be about us not him — with a focus on the policies, anxieties and problems of regular people.

Moreover, many women I’ve spoken with, in both parties, told me there’s a subtle sexism implied by the whole line of attack: Whatever her role in defending Bill Clinton’s misdeeds over the year, Hillary Clinton, not her husband, is the one running for president.