Perhaps the biggest subplot of the third Republican primary debate will be the interactions between DeSantis and Haley. They have emerged as the two main alternatives to Trump at this point. DeSantis, of course, started off his campaign as one of the front-runners, and while he has steadily declined in the polls over the last several months, he remains in second place nationally with 14% support, according to 538's national polling average. He's also in second place in the key early state of Iowa.

However, Haley has risen in the polls in recent months, and she's now in second place in two other key early states, New Hampshire and South Carolina.

With only five candidates qualifying for the debate, each of them will get more speaking time and the stage will feel more intimate. That could provide DeSantis and Haley with more opportunities to attack each other. According to polling from 538, The Washington Post and Ipsos, Republican voters have generally thought both DeSantis and Haley performed well in the first two debates.

But if one of them clearly bests the other on Wednesday night, that could be the differentiator that both of them are looking for.

-Analysis by Nathaniel Rakich of 538

The two-hour debate will feature four planned segments.

The "national security implications" of the Israel-Hamas and Russia-Ukraine wars will be a focus, along with domestic political issues, according to NBC News.

The moderators are also expected to reference campaign developments that NBC News reporting and polls show are of interest to voters, per organizers.

Candidates will have 90 seconds to answer each question, as well as 60 seconds to answer follow-up questions.

At the end, candidates will have 60 seconds to give a closing statement.

-ABC News' Meredith Deliso

With five candidates set to clash on the debate stage, all eyes will be on how they respond to Tuesday night's relatively poor election results for Republicans, including if they'll take swipes at Trump's status as party figurehead.

Much of the action is anticipated to take place near center stage between DeSantis and former South Carolina Gov. Haley, who have been running neck-and-neck in the polls for second place and who are seeking to grab the mantle of Trump alternative for a segment of the party that remains skeptical of the former president.

Still, it's unclear how much the event will move the needle -- Trump retains gargantuan leads in national and early state polling, per 538's average, and has seemingly suffered no consequences from GOP voters by skipping the first two debates, a trend he'll continue Wednesday.

Read more about the key questions for the evening here.

-ABC News' Tal Axelrod

It’s been nearly six weeks since the candidates vying for the Republican nomination last met on the debate stage.

A lot has happened since then.

Former Vice President Mike Pence suspended his campaign, prompting audible gasps when he made the announcement on stage last month at the Republican Jewish Coalition's Annual Leadership Summit in Las Vegas. He was the first major candidate to drop out of the race.

Two other hopefuls failed to reach the Miami debate stage: North Dakota Gov. Doug Burgum and former Arkansas Gov. Asa Hutchinson. That means Wednesday’s debate will be the smallest of the three, with just five candidates in the spotlight.

One thing hasn’t changed, though, and that’s Trump’s commanding lead over the GOP field.

While the former president is once again snubbing his opponents, he won’t be too far away as he holds his own rally in Hialeah, Florida.

-ABC News' Alexandra Hutzler

Scott, who is trailing the other debate participants in the polls, hopes to make his mark among voters looking for an alternative to Trump, a campaign spokesperson said ahead of the debate.

"At the end of the day, I think what I would expect from Sen. Scott is asking -- who can win?" Matt Gorman, a senior campaign adviser, said on ABC News Live Wednesday. "Is it gonna be a moderate who's coalescing the 'Never Trumpers' like Gov. Haley, or someone who's fallen two-thirds in the polls like Gov. DeSantis, whose only thing that's consistent about his campaign is how much it's underwhelmed?"

Gorman said Scott might look to focus on contrasts among the candidates on policy issues such as abortion. The senator has said that as president he would advocate for a 15-week national ban on abortion.

-ABC News' Meredith Deliso