MIAMI (AP) — New divisions erupted in the Republican Party’s presidential contest on Friday amid competing calls for party unity as the GOP scrambled to blunt Donald Trump’s momentum.

Trump intensified his insistence that party leaders embrace his candidacy while unveiling a significant new ally at a press conference at his Palm Beach resort. Standing at Trump’s side, retired neurosurgeon Ben Carson endorsed his former GOP rival and warned that a failure to rally behind him would “fracture the party in an irreparable way.”

Carson said Friday that he and Trump “buried the hatchet” after months of political wrangling, describing the front-runner as a “very cerebral” person.

Florida Sen. Marco Rubio, fighting for his political life ahead of his home state’s pivotal Tuesday primary, charged that Trump himself could destroy the party given the many Republicans who vow never to support the New York real estate mogul.

“I certainly think it would fracture it,” Rubio said of a Trump nomination on CBS’s “This Morning. “There is a very significant number of Republicans that will never vote for him. And you can’t win unless the party’s united.”

The fresh signs of GOP chaos follow a surprisingly civil debate Thursday night days ahead of high-stakes primary elections in Florida and Ohio.

A restrained Trump used the latest presidential debate to send a none-too-subtle message to Republicans still wary of his insurgent candidacy: “Be smart and unify.” Cruz and Rubio toned down their rhetoric, too, concluding that all-out attacks against Trump didn’t work.

“I can’t believe how civil it’s been up here,” Trump declared at one point in Thursday’s face-off of the GOP’s final four.

The candidates now charge out of Miami with four days left to make their final arguments before next week’s all-important big-state presidential primaries.

Trump was heading to St. Louis and Chicago after appearing with Carson; John Kasich headed for his must-win home state of Ohio; Rubio made his home-stand in Florida and Cruz was shuttling from Florida to Illinois.

In all, 367 Republican delegates are at stake Tuesday in Illinois, Missouri, North Carolina, Ohio and the Northern Mariana Islands, a delegate haul that could go a long way toward determining the GOP nominee.

Democrats Hillary Clinton and Bernie Sanders, too, will be competing on Tuesday, with Clinton out to regain momentum after her startling loss to Sanders in Michigan this week.

Trump’s rivals, in a desperate scramble to halt his march to the nomination, gradually ramped up their criticism as the latest debate wore on.

Cruz, eager to cement his position as the party’s last best alternative to Trump, had a string of criticisms of the GOP front-runner, too, saying flatly at one point: “His solutions don’t work.”

When it was over, Trump pronounced it an “elegant” discussion. He was clearly intent on projecting a less bombastic — and more presidential — image.

“We’re all in this together,” he said early on, sounding more like a conciliator than a provocateur as he strives to unify the party behind his candidacy. “We’re going to come up with solutions. We’re going to find the answer to things.”

The candidates split down the middle — Trump and Cruz vs. Rubio and Kasich — on the likelihood of the GOP race coming down to a contested Republican convention this summer.

“I think I’m going to have the delegates, OK?” Trump said.

As for who has a realistic chance of winning the nomination, Trump simply wrote off Rubio and Kasich, saying, “There are two of us that can, and there are two of us that cannot, OK?”

Rubio countered that disappointing “delegate math” aside, he’d keep on fighting.

“As far as Florida’s concerned, we feel good, we’re making progress, we have real momentum here now,” Rubio said Friday.

Kasich, for his part, said it wouldn’t be so bad to have a contested convention. He added there are plenty of primaries left so “let’s not get ahead of ourselves.”

Trump was questioned about whether he had set a tone at his rallies that fueled violent encounters between supporters and protesters.

On Friday morning, he said it was “appropriate” for his supporters to lash out with violence against protesters.

Pace reported from Palm Beach, Florida.