MIAMI — President Donald Trump will be just a few keystrokes away from sending rhetorical airstrikes into the middle of the Democrats' first 2020 presidential debate here on Wednesday night.

The top two contenders for the party's nomination according to the polls, as well as the fourth- and fifth-place candidates — former Vice President Joe Biden, Sen. Bernie Sanders of Vermont, Mayor Pete Buttigieg of South Bend, Indiana, and Sen. Kamala Harris of California — will be looming in the wings as possible targets before the second-night showdown on Thursday.

And armies of campaign operatives, pundits and Twitterati will be spinning the results electronically in real time.

Ultimately, the biggest presences in this first debate may not be physically in the room.

For most of the candidates actually on the stage, the basic challenge Wednesday will be introducing themselves to an electorate that has shown little interest in them so far.

Of the 10 candidates on stage Wednesday night, only Sen. Elizabeth Warren of Massachusetts (third-place in the polls), former Rep. Beto O'Rourke of Texas and Sen. Cory Booker of New Jersey regularly register above 1 percent in national polls. That means — deep breath — former HUD Secretary Julián Castro; Sen. Amy Klobuchar of Minnesota; Rep. Tulsi Gabbard of Hawaii; Washington Gov. Jay Inslee; New York Mayor Bill de Blasio; Rep. Tim Ryan of Ohio; and former Rep. John Delaney of Maryland still have to introduce themselves to most voters, and turn them into fans fast.

For some, the handful of minutes they get to speak will surely feel like bite-size infomercials. But the need to differentiate means just about anything could happen.

O'Rourke has a lot riding on his performance, and he'll be sandwiched in a potentially uncomfortable spot.

He'll be literally betwixt and between Warren and Klobuchar — two decidedly substantive and accomplished rivals — on the stage. O'Rourke's supporters insist that his turn as a glamor candidate earlier in the campaign doesn't mean he lacks policy chops, but he's been criticized for having a thin record of accomplishment compared to some of the women running who drew less attention at first.

Download the NBC News app for full coverage of the first Democratic debate

His ability to hang with them on substance will surely be put to the test Wednesday night.

During a two-hour flight here from Washington on Tuesday, Klobuchar immersed herself in a set of thick three-ring binders with pink soft-plastic covers, pausing to write longhand notes on index cards. She told NBC News that she wants to make sure that she can draw attention to the issues that she has put at the center of her campaign, including lowering the cost of prescription drugs for consumers.

Warren is determined to let voters know that she intends to make the economy and the political system work better for many people through "big, structural change," a campaign aide said.

The good news for O'Rourke is that he has an opportunity to show he can handle himself against tough competition after having been caricatured as a candidate armed with a toothy grin and little to back it up. The bad news is there's a chance that Warren, who is in the top tier of contenders, and Klobuchar, who is eager to stand out, could eviscerate him by dint of comparison.

O'Rourke's fate is just one of many subplots that will play out during the two-hour contest of wits, which will air on NBC, MSNBC and Telemundo beginning at 9 p.m. ET. After nearly six months of campaigning, it's the first time Democratic voters will get to see candidates competing against each other directly.

Warren is trying to build on the momentum she's created in national and state-level polling. The debate should offer some clues as to whether she will be able to sustain it — a question that will also be answered in part by the performances Thursday of Biden and Sanders, who sit ahead of her in most surveys.

Booker, who has won praise for his ground operations in Iowa and South Carolina from local political insiders, has not seen a payoff so far in surveys. Like O'Rourke, he needs to keep donors and voters interested in a campaign that hasn't taken off yet. That may require him to be more aggressive — not only toward the candidates on the stage and Trump but perhaps toward those who debate Thursday night.

Looming over all of the discussion will be Trump, who may decide to play a version of "Mystery Science Theater 3000" by weighing in from the Twittersphere. And the four candidates in the top 5 who aren't on the stage until Thursday — Biden, Sanders, Buttigieg and Harris — won't be far from mind, either.

It's not clear how much the Wednesday night candidates will want to risk going after the Thursday night candidates — who will have 24 hours to formulate responses — but there are a host of issues that could prompt volleys. For example, Booker has taken Biden to task for fondly remembering his personal relationship with segregationist Sen. James Eastland, D-Miss., last week. Biden portrayed himself as an opponent of Eastland on policy, which was true in some cases but not in others.

Since then, NBC News reported that the Senate adopted a Biden amendment in 1975 designed to ensure that schools that maintained segregated classrooms — white children in one class, black children in another — did not lose federal funding as a result, and The New York Times published a report Wednesday about Biden's work with Eastland and others on a series of crime laws that led to what critics have called the "era of mass incarceration."

There can be little doubt that each campaign will claim afterward that its candidate had the "breakout" moment that will positively and permanently alter his or her trajectory in the nomination fight. But most, if not all, will be wrong.

The bar for that — like O'Rourke's challenge in sticking with Warren and Klobuchar — will be high.

Even a split decision might leave him no better or worse off than he is now — which is sixth place in the Real Clear Politics average of national polls at 3.3 percent.

"I could see a situation where a Klobuchar or a Warren rack up points on substance, but Beto O’Rourke gives a great answer to a question that allows his team to claim some victory," said Rodell Mollineau, a former Senate leadership aide and a partner at the public relations firm Rokk Solutions. "You have an opportunity to win on one or the other, and the ultimate winner will be the one who can win on both."