As an unshackled Donald Trump slouches towards Election Day, it's Hillary Clinton who may face the tougher task at Wednesday's final presidential debate in Las Vegas.

It's been 439 days since Trump took the stage at the very first Republican primary debate in August 2015, heralding many of the storylines that have dogged him throughout his entire candidacy. Many of the red flags raised that day, including his misalignment with the GOP, his business record, and his relationship with women, have been reincarnated during the general election campaign: his attacks on Paul Ryan and John McCain, a tax return that showed him taking a billion-dollar loss, and the now infamous "Access Hollywood" tape.

It's been even longer since the The New York Timesbroke the news that Clinton had used a private email server during her time as secretary of state, also forecasting what would become a dominant issue of her bid. Wednesday evening, it won't only be Clinton's emails that are a topic of conversation but also those of her campaign chairman, John Podesta, whose hacked communications WikiLeaks has been releasing.

Subsequent allegations of sexual abuse have kept the Trump tape story alive, but they are unlikely to prove more enlightening. 

"The accusations that have come out from the women is the second act in a play that's already begun," said John Donvan, an ABC News correspondent who's a student of the presidential debate system. "The tape was the first act, but we know what the play's about now."

Not so with Clinton, who has more at stake Wednesday night. That's because she leads her opponent by several points in the polls, and markets give her roughly 90% odds at becoming the next president

The former secretary of state has kept her head down in recent days, preparing for the debate and allowing her candidate's missteps to dominate the news cycle. Tonight, though, she will have to answer the many questions that have arisen from the WikiLeaks emails, the authenticity of which her campaign has thus far refused to confirm or deny.

"There's fresh stuff that Wallace can pull out," said Donvan, referring to Fox News' Chris Wallace, who will moderate the debate. "There's almost nothing left that Donald Trump can do to shock anymore."

That's not to say that Wednesday's debate won't be relevant for Trump.

The real estate magnate has lost significant ground in the polls recently, and some have nearly written off his candidacy. House Speaker Ryan, after the last debate, essentially told congressional Republicans to go their own way on Trump.

"If I was Donald Trump, I would go into this debate and try to be exceptionally professional," said Steve Schale, a Democratic strategist based in Florida. "The problem he's got right now is that he is a side show, and everything he does seems to reinforce that."

Trump's unorthodox tactics include claiming that numerous dead people vote, that Clinton should be drug tested ahead of the debate and insisting that the system is rigged against him.

His camp has announced he will be bringing President Barack Obama's half-brother, who supports Trump, to the debate hall. (Last debate, he brought with him three of President Bill Clinton's sexual assault accusers.) The move signals a reformed Trump may not be on deck for tonight.

"I expect him to double down on crazy," said Schale.

For both candidates, the debate will mark a last chance to address a broad swath of the American electorate, said Chris Arterton, professor of political management and former dean at George Washington University's Graduate School of Political Management. While it might be nice for them to get into the weeds on some of their policies and proposals, it is improbable.

"Can they get out the kind of tit for tat complaints about each other and the kind of candidacy that they have each adopted and speak to a broader audience?" said Arterton. "I think it's entirely unlikely that they will do that."

Donvan, who moderates the Oxford-style Intelligence Squared U.S. debate series and is part of a petition promoting the reform of the American presidential debate system, attributes part of the problem to the format of the event itself. Simply put, it doesn't lend itself to actual debate.

"What we really see is simultaneous interviews," he said.

The entire election cycle has been disappointing from the point-of-view of actually presenting a debate, he said. "A debate is an argument, which is very different from bickering," he said.

Some on the left have raised concerns over Wallace's ability to be fair, given the Fox network's political leanings. Schale said such worries are overblown.

"Wallace wants to be seen as a real journalist and not a Fox News journalist," he said. "He'll probably go over and beyond the call of duty to try and call this thing straight."

The first debate between Clinton and Trump spurred a clear shift in Clinton's direction in the polls. The second debate did not. The third round will be a chance for the former New York Senator to solidify her position as the leader, and it is hers to win or lose.

"This is the last opportunity for a stumble, but I don't expect that there's any chance she will stumble," said Schale.