Donald Trump’s rivals tried to make the most of their final debate with the Republican presidential front-runner before next week's Super Tuesday II slate of primaries — with do-or-die contests for Marco Rubio and John Kasich in Florida and Ohio, respectively — but whether it changed minds or won over enough undecideds to influence the outcome remains to be seen.

First out of the gate Friday was Trump, who got the endorsement of former rival Dr. Ben Carson, who said he forgave Trump -- "the Christian thing to do" -- for any campaign attacks and praised him as a man whose public image belies his true character, describing him as a far more “cerebral” candidate than he’s given credit for. His endorsement appears to serve as a counterweight to Carly Fiorina coming out for Ted Cruz earlier this week.

At the Miami debate Thursday night, Trump summed up the reality, though, that Florida Sen. Rubio and Ohio Gov. Kasich face.

He said only “two of us” can get the delegates to win – meaning Trump and Cruz — and “two of us” cannot, referring to Rubio and Kasich.

“That is not meant to be a criticism … that’s just a mathematical fact,” Trump said, urging the party to “be smart and unify.”  

Rubio and Kasich are vowing to win their home states, which dish out all their delegates to the primary night winner.

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But even if they win, their paths to the nomination remain unclear – and their best angle may still be to try and deny Trump the delegates needed to clinch the nomination going into the convention in July.

But Trump strongly suggested that as early as next week, the GOP contest could winnow down to a two-man race.

The states holding primaries Tuesday are Ohio, Florida, Missouri, Illinois and North Carolina.

The CNN-hosted debate Thursday saw Rubio change up his campaign approach once again – dialing back the personal attacks on Trump, which didn’t do much for his numbers in the most recent round of contests.

Instead, Rubio hit Trump on more substantive issues.

One of the most pointed debate clashes came over the diplomatic thaw with Cuba — a huge issue in Florida, host of the CNN debate and next week’s critical primary. Trump tangled with his rivals as he claimed he’s “in the middle” on the issue.

Trump said “something” should take place after a decades-long freeze, but, “I want to get a much better deal.”

“Here’s a good deal,” Rubio snapped back. “Cuba has free elections. Cuba stops putting people in jail.”

He – along with his rivals – did their best Thursday to draw distinctions between them and Trump.

Oftentimes, Trump seemed to lean on his “art of the deal” to explain his approach to global challenges. But it earned him criticism from the others on stage.

Cruz hammered Trump for suggesting he’d be able to re-negotiate a nuclear deal with Iran.

“I will rip to shreds this catastrophic Iranian nuclear deal,” Cruz countered.

Trump also took heat from Rubio and others as he defended his claim that “Islam hates us.”

The Republican front-runner said there’s “tremendous hatred” in the Muslim world and called for new laws to confront the threat.  

“We better expand our laws or we’re being a bunch of suckers, and they are laughing at us,” Trump said. 

But Rubio and Cruz both said “of course” they would not want to allow the targeting of family members of terror targets, as Trump has called for. And they chided him for his remarks. 

“The answer is not scream all Muslims bad,” Cruz said. 

“The problem is presidents can’t just say whatever they want,” Rubio said. “I’m not interested in being politically correct. … I’m interested in being correct.” 

Trump’s rivals noted America must work with other Muslim nations to confront the ISIS threat.

For the most part, Trump and his three Republican presidential rivals held their personal fire Thursday night during their last debate before next Tuesday's primary in Florida – which votes alongside four other states.

Trump even remarked on the subdued tone: “So far I cannot believe how civil it’s been up here.”

"I think it was good that we had a substantive debate," Cruz told Fox News' Megyn Kelly. "The last two debates were pretty ridiculous [and] I was glad to see that nonsense ending."

Ohio Gov. Kasich also stressed at the debate that he’s run an “unwavering positive campaign” all along.

But on the domestic front, they did battle on the best way to save Social Security -- with Trump breaking from his competition by saying he'd leave it alone despite warnings it would start running out of money in two decades.

“I will do everything in my power not to touch Social Security,” Trump said. He said he’d instead get rid of waste, fraud and abuse — including by ensuring the government bids out contracts. 

Rubio, though, said, “You’re still going to have hundreds of billions of dollars of deficit that you’re going to have to make up.” He called for gradually raising the retirement age to 70.

Cruz echoed that call, saying the program is “careening toward insolvency.”

“We need to see political courage to take this on and save and strengthen Social Security,” he said. 

Kasich also called for changes, though not necessarily to the retirement age.

As Trump consolidates support and builds his delegate lead, though, he kicked off the debate with a pointed message to the so-called “Republican establishment,” effectively telling them to get on board with his campaign.

He started his opening statement by claiming his campaign is bringing in Democrats, independents and others in huge numbers to the polls.

“The Republican establishment, or whatever you want to call it, should embrace what’s happening,” he said, addressing tension between his campaign and senior GOP leaders. “We are going to beat the Democrats.”