MIAMI – Donald Trump promised a softer side as he and his three remaining Republican rivals prepared to square off Thursday night in their final debate before next week’s all-important big-state presidential primaries. He also vowed to “finish off what you have to finish off” – raising questions about which Trump would show up.

Each of the candidates had an urgent mission as the Miami GOP debate gave them one last chance to put their case to a televised audience of millions before voters in Florida and four other states dish out a trove of delegates Tuesday. Those elections will go a long way toward determining the outcome of the primary season.

A CNN staffer walks across the stage where the Republican presidential debate sponsored by CNN, Salem Media Group and the Washington Times will take place, at the University of Miami, on Thursday in Coral Gables, Fla.

Ted Cruz was seeking to cement a position as the party’s last, best alternative to Trump. Marco Rubio was out to save his flagging candidacy by energizing voters in his home state of Florida. John Kasich was hoping his above-the-fray strategy would finally pay off.

Trump, for his part, was itching to give his front-runner’s campaign a giant thrust toward the nomination by dominating his dwindling cast of rivals.

Republican National Committee Chairman Reince Priebus said in advance he was hoping for a more “G-rated debate” than the last Republican face-off, a week ago, when the candidates engaged in a two-hour brawl that featured shouting, insults and even sexual innuendo.

President Barack Obama, offering political commentary from the sidelines, said the party was going through a “Republican crackup” that had taken on the tone of a “circus.” Obama rejected any notion that his own actions or policies were to blame for the polarized political climate.

Instead, he blamed GOP forces for fostering the idea “that cooperation or compromise somehow is a betrayal” and for pushing “maximalist, absolutist positions.”

TRUMP: IMPERATIVE TO WIN DRIVES HIS BEHAVIOR

Trump told CNBC on Thursday that the imperative to win the Republican nomination had made him “not necessarily as politically correct and even as nice as you would like to be as a person.”

“It’s ending fairly soon,” he predicted, adding that he would then be more of a unifying presence.

Earlier in the week, he’d pledged a “softer” debate in Miami, but he also made his vow to finish off what he’d begun.

While Trump talks about showing a softer side, some of his rallies have had a harder edge, with the candidate at times seeming to encourage physical altercations with protesters. At a rally in Las Vegas, for example, he said he’d like to punch a protester in the face. On Wednesday, a man was charged with assault for attacking a protester who was being escorted out of a Trump rally in Fayetteville, North Carolina.

Rubio, Trump’s chief antagonist, has been rethinking his tone.

After mocking the billionaire businessman on everything from a bad spray tan to his spelling to his “small hands,” the Florida senator admitted to having regrets about going too far.

“It’s not something I’m entirely proud of,” Rubio said during a town hall-style appearance on MSNBC. “My kids were embarrassed by it, and if I had to do it again, I wouldn’t.”

Florida is the biggest prize of Tuesday’s five-state round of voting, and all 99 of the state’s delegates will go to the winner.

IN ALL, 367 DELEGATES AT STAKE TUESDAY

In all, 367 Republican delegates will be at stake, with voting also occurring in Illinois, Missouri, North Carolina, Ohio and the Northern Mariana Islands.

Earlier Thursday, Cruz intensified his efforts to coalesce the anti-Trump vote, and showcased his first Senate endorsement, from Mike Lee of Utah, a tea party conservative.

“Defeating Donald Trump is critical to putting a conservative in the White House and reversing the disastrous eight years of Barack Obama’s presidency,” Cruz wrote in a pre-debate fundraising appeal.

Cruz has few friends among Republicans in the Senate. He angered many in the Republican ranks when he took the unprecedented step of standing on the Senate floor and calling Majority Leader Mitch McConnell, R-Ky., a liar. Several in the Republican Party also hold Cruz responsible for helping to engineer the 16-day partial government shutdown in 2013 in an unrealistic effort to force Obama to back down on his health care law.

SENATORS HESITATE TO BACK CRUZ

As Rubio’s fortunes declined this past week and some in the Republican Party suggested that the establishment rally around Cruz, few senators were willing to step forward. Lindsey Graham of South Carolina and Dean Heller of Nevada raised the possibility of Cruz as the alternative, but others stood firm in their support for Rubio and declined to even discuss the prospect of Cruz as their choice.

Ohio Gov. Kasich, who has tried to stay out of the name-calling, pinned his hopes of survival on bringing home the 66 delegates in his state’s winner-take-all primary. He has yet to win anywhere.

Trump’s message to his rivals and the establishment figures opposing his candidacy: Accept the inevitable.

“They should embrace what I’ve done,” he told CNBC, citing the surging numbers of Republicans turning out to vote in primaries and taking credit for high TV ratings for the Republican debates.

Earlier in the week, he predicted that if he wins Florida and Ohio, “it’s over.”

Benac reported from Washington. AP Writer Donna Cassata in Washington contributed to this report.

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