Hillary Clinton and Donald Trump are preparing for their highly anticipated Monday night debate showdown in ways that appear to be as different as their candidacies. One looks to be hunkering down with homework, research and rehearsals, while the other seems to be taking an on-the-fly casual approach to what could be the most important 90 minutes of the presidential election.

The first presidential debate could easily become one of the most watched events ever, and it will be nearly impossible to avoid seeing at least some parts of it on a television screen, cell phone, tablet or laptop or social media.

Here’s what we know about how they are preparing:

Hillary Clinton

Between her 2000 Senate run and two presidential bids, Clinton has appeared on the debate stage nearly 40 times. Still, she has never prepared for an opponent quite as unpredictable as Trump.

In an email to supporters this week, Clinton touted her debate experience but acknowledged Monday’s matchup is "the most important” yet.

This month, Clinton has hunkered down with top aides to study from the comfort of her own home. The bulk of Clinton’s prep has been done in and around her house in Chappaqua, New York, partly due to her recent bout with pneumonia.

Related: How to Watch Monday's Presidential Debate

Following the disclosure of her illness, Clinton took three full days off the trail to recover and read up on briefing books.

And while the campaign is very tight-lipped on specifics, aides say they are preparing for the night to go in several directions.

The candidate herself has often said that she doesn’t know “which Donald Trump will show up” to the first debate. Clinton's communications director, Jennifer Palmieri told reporters this week that the campaign is “preparing for the different Trumps that might show up."

At a Hamptons fundraiser last month, the former secretary of state asked the crowd for “thoughts or ideas” on her debate strategy against the Republican nominee. "Maybe he will try to be presidential and try to convey a gravity that he hasn't done before or maybe he will come in and try to insult and try to score some points,” she speculated.

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Recently, Clinton has vowed to “communicate as clearly and fearlessly” as possible “in the face of the insults and attacks and the bullying and bigotry that we’ve seen coming from my opponent.”

Those familiar with her prep know she needs to be ready to take on any uncomfortable topics that Trump could possibly throw her way, a tactic Trump hasn't shied away from in the past.

Aides argue Clinton has a slight edge because she has so much experience debating one-on-one, whereas Trump spent most of the time in the primary season sharing the stage with many opponents.

Related: Clinton Preparing for 'Different Trumps' at First Debate

The Democratic nominee opted for a fairly light schedule this week in order to practice for the debate. She only traveled to two battleground states — Pennsylvania and Florida — in order to accommodate enough prep time. She’s taking full days off the trail Thursday and Friday, unlike her opponent, and has no public events scheduled over the weekend either.

One very guarded secret that has stayed under wraps, so far, is the question of who is playing Trump at these private sessions. Some have hinted that multiple people are taking on the role, in order to best prepare for the different tones Trump may strike.

Palmieri has called the debate stage a “great place” for voters to hear from Clinton in an “unfiltered” way.

The critical calculation will be: How much time can Clinton spend on the offensive debating against someone like Trump who will seek to put her on defense for most of the 90-minute discussion.

Every campaign tries lower expectations for their candidate ahead of a debate, and then pump up their performance afterwards, but Democrats are preparing for the spin wars to be especially important this year in shaping the public image of the debate.

One of Clinton allies’ biggest concerns is that Trump will be judged against an unusually low bar, while Clinton will be judged against an impossibly high one. Aides have already started working the refs, urging reporters and pundits to hold Clinton and Trump to the same standard, and her campaign is sure to flood the airwaves with surrogates ready to declare Trump’s performance a disaster and shame media figures whom, in their opinion, are too soft on Trump.

Hillary Clinton (L) and Bernie Sanders during a Democratic debate in New York in April 14. LUCAS JACKSON / Reuters

As the countdown clock to Monday night’s first encounter ticks away, Clinton told radio host Steve Harvey Tuesday that she’s ready for a heated encounter on the debate stage.

“I can take it,” she said. “I can take that kind of stuff. I’ve been at this and I understand it’s a contact sport.”

Donald Trump

The Trump team has been largely mum about his debate prep plans. The GOP nominee is often on the trail — usually only taking Sundays as his fully day off — making time dedicated solely to preparation scarce.

In fact, the weekend leading up to the first debate was originally devoid of campaign events, allowing for debate prep on both Saturday and Sunday but the campaign has now added a rally stop in Virginia for Saturday evening. Trump will do debate prep this weekend with advisers including New Jersey Gov. Christ Christie, campaign CEO Steve Bannon, campaign manager Kellyanne Conway, retired general Mike Flynn and former NYC Mayor Rudy Giuliani.

But while details about his preparation have been rare, the candidate himself has been more than vocal about his views on the moderators (he doesn’t think there should be any and is skeptical they’ll be fair to him) — and how he’ll treat the rival he’s sharing the stage with.

In a Monday evening interview with Fox’s Bill O’Reilly, Trump said he doesn’t think he’ll attack Clinton personally, despite his past jabs at Clinton and her husband, Bill, for his past marital indiscretions. "I don’t know what I’m going to do that exactly,” Trump said. "It depends on what level she hits you with, if she’s fair, if it’s unfair, but certainly I’m not looking to do that.”

Instead, he says he’s planning on taking the stage with the intention of being respectful. "If she treats me with respect, I will treat her with respect. It really depends. People ask me that question, ‘oh you’re going to go out there and do this and that. I really don’t know that. You’re going to have to feel it out when you’re out there. She’s got to treat me with respect. I’m going to treat her with respect. I’d like to start off by saying that because that would be my intention.”

The GOP nominee has been fond of describing himself as a “counter-puncher,” but Trump’s debate strategy during the primary seemed simply to keep punching at rivals while reiterating portions of his stump speech. He sparred with nearly every Republican who he shared the stage with throughout the GOP primary process and mostly stayed away from specific policies in lieu of rhetorical red meat for his supporters. And he was generous with his use of nicknames for his opponents: “low energy” Jeb Bush, “lyin’ Ted” Cruz and “liddle Marco” Rubio.

And primary debates were always negotiable, not absolutes. When Trump didn’t want to debate before the Iowa caucus, he dropped out, questioning Fox New’s ability to be fair to him after his comments about one of its lead anchors, Megyn Kelly, having “blood coming out of her wherever.”

In fact, whether or not Trump would actually stand center stage during the primaries was often a question. At rallies or in interviews he tended to casually float the idea that he might not show up on the debate stage. In the end, he showed up to all but one.

Ben Carson, Donald Trump and Ted Cruz at a Republican debate in December. Justin Sullivan / Getty Images

Now that Trump’s in the general, that strategy doesn’t seem to have changed that much. When asked Monday night if he’d appear in the debates hosted by CNN’s Anderson Cooper and ABC’s Martha Raddatz, Trump said he’d "show up” but that “they’re gaming the ref” after Matt Lauer was criticized for being too soft on him during NBC’s Commander in Chief Forum earlier this month.

"They hit Matt because they said he should have been much tougher. Well, he couldn’t have been much tougher. What they are doing is they are gaming the system, like gaming the ref,” Trump alleged.

Throughout, Trump maintains that his “whole life has been a debate,” which readies him for the approaching moment.