Coming into this debate, these five Republican candidates had different missions -- some wanted to just stay alive, while others wanted to break through and maybe, just maybe, close the gap with Trump.

For DeSantis, it was about the latter goal. And on the whole, he seemed very on his game in his home state debate. He took the occasional dig at Trump, like saying he'd actually get Mexico to pay for the wall, which Trump said he'd do but failed to accomplish as president. Throughout the debate, DeSantis often pivoted to immigration and financial concerns in his answers, which was wise as polls show those are principal concerns for Republicans.

On the other end of the spectrum, Christie was looking to remain relevant in this campaign. And while he's made his name as the most anti-Trump candidate in the GOP primary, he mostly avoided talking about Trump in Miami.

Now, the major focus on foreign policy and immigration as topics may have helped Christie by keeping away from topics that would lead him to go after the former president. Could this buoy Christie's numbers just a little? Hard to say, given that he's got terrible favorability numbers among Republicans, who are generally pro-Trump in their views. But it was a change for Christie from what we've seen in previous debates.

-Analysis by Geoffrey Skelley of 538

This was a substantive debate, with in-depth exchanges on topics as wonky as Social Security and ships in the Navy. It wasn’t nearly as chaotic and negative as the last debate, although perhaps the headline was the emerging rivalry between Haley and Ramaswamy, who went out of their way to attack each other throughout the night. To me, it seemed that Haley got the better of those exchanges, as Ramaswamy came off as too aggressive. But we’ll know for sure what Republican voters thought when we get the results of the next 538/Washington Post/Ipsos poll on Thursday.

-Analysis by Nathaniel Rakich of 538

While five of his primary challengers were on stage in Miami debating each other and sometimes pointedly attacking him, Trump was rallying supporters in nearby Hialeah, Florida, a heavily Hispanic community.

The former president's remarks tied his familiar attacks on his legal troubles -- he denies all wrongdoing and has pleaded not guilty in four criminal cases -- to the language of being persecuted like in "communist Cuba," in what appeared to be a push to galvanize the local audience.

“We have some great Cubans here,” he said.

He also repeated his recent campaign rhetoric about keeping America and the world safe and peaceful, insisting that under his watch, attacks against Israel and the Russia-Ukraine war would not have happened.

Of the debate, he said, “Nobody's talking about it. Everybody's watching this.”

Hialeah Mayor Esteban Bovo was also invited on stage by Trump where Bovo announced he will ask the City Council to authorize a street named after Trump.

-ABC News’ Lalee Ibssa and Soo Rin Kim

After the debate, the South Carolina senator was seen taking a photo with a blonde-haired woman. The two were physically affectionate, including with their hands interlocked -- and Scott, later asked by a reporter who it was, said, "Oh, my girlfriend."

Scott had said in September that he was dating someone -- "a smart, Christian woman" -- while declining to bring her on the trail, saying that he would introduce her "at some point."

"I have been very protective of my family and my loved ones," he told The Washington Post in September. "I signed up for this. If we make it, she will be signing up for it as well, but at least then she'll know what she's getting into."

-ABC News' Gabriella Abdul-Hakim, Libby Cathey and Fritz Farrow

After a commercial break, candidates were asked about what they would do to stop the flow of fentanyl into the country.

Many of them took aim at China and what was being brought into the U.S. across the border. Scott called for closing the southern border, and DeSantis repeated his argument for using military force against the drug cartels, which has drawn criticism from some who say it would be untenable as the cartels are in a foreign country that is an ally. Ramaswamy rejected the term "overdose" when it comes to fentanyl, instead calling it "closer to bioterrorism" that warrants an aggressive response.

Christie and Haley also addressed the need for more treatment options for those struggling with addiction.

"For every family there tonight who has lost a loved one to fentanyl or to any other type of opioid overdose, what you know is all you want is a chance for them to win their lives back," Christie said. "When I'm president of the United States, we're going to call this what it is. It is a disease. Like heart disease, diabetes or any other disease like cancer that can be treated, should be treated. We not only have to stop supply, but we have to lower demand and save lives."

Haley said she agreed with the former New Jersey governor and that the focus should also be on mental health and addiction centers.

-ABC News' Alexandra Hutzler