MIAMI. Fla. - The Republican Party's four remaining candidates are facing off at the University of Miami on Thursday for their last debate before critical races in five states and one territory on March 15.
Of particular importance in Tuesday's races are winner-take-all contests in Ohio and Florida that will go a long way to determining whether front-runner Donald Trump can put the race away outright or whether his rivals can force a contested convention in July.
With time running out to stop Trump, the debate is another crucial opportunity for the GOP field to make their case.
Here are four things to watch at tonight's debate, hosted by CNN, Salem Media Group, and the Washington Times.
Trump's roll to the nomination
Just like the last several debates, the main question will be whether the candidates can slow Trump's momentum. So far the business mogul has been unstoppable; he has continued to win states and expand his delegate lead while facing continuous pressure from his rivals and aggressive fact checks from debate moderators.
Trump's responses to recent attacks on his business record and positions have been outrageous and astoundingly inconsistent. After last week's GOP debate, Trump backed down from his boast that he would force Americans to commit war crimes (he says he'd change U.S. law first, and then torture people) and the campaign also had to clarify his wild swings between praising high-skilled work visas and promising to crack down on them. Along the way, he appeared to abandon his calls for sweeping government aid to provide health care for the uninsured in favor of a vague plan in line with typical GOP doctrine.
It's hard to know what Trump would do as president based on his public statements. Nonetheless, the results of Saturday's primary contests where Trump easily won Michigan and Mississippi were clear: Republican voters like what they hear. Unless that changes soon, he will become the nominee.
Rubio's last stand
Sen. Marco Rubio's support crashed through the floor in Saturday's primaries and his campaign looks to be on its last legs. Unless something drastic changes in the next few days, he's unlikely to make it to another debate.
Rubio is banking everything on winning Florida on Tuesday and urging the party to help him do it if only to deny Trump its 99 delegates, but several polls this week show Trump leading by more than 20 points. Even if the Florida senator manages to pull off an upset, a la Bernie Sanders in Michigan, his delegate path to the nomination appears to be closing.
Rubio's collapse has coincided with his recent shift to an all-out war on Trump; the senator admitted on Wednesday that some of his more juvenile insults had made him and his family uncomfortable at times. Still, Rubio will be likely to press the attack on issues like the lawsuit-plagued Trump University.
Cracks in the anti-Trump coalition
Sen. Ted Cruz is challenging Rubio in Florida, looking to quickly remove the Florida senator from the race. A pro-Rubio super PAC is running ads against Gov. John Kasich in Florida and Illinois.
With that kind of pressure, there is some motive for the non-Trump candidates to swipe at each other and not just the front-runner. Since Rubio's swing against Trump, the candidates have kept an informal truce, but it's a fragile one. Rubio and Cruz have fought in the past over issues like immigration and national security, and it's not hard to see how those fissures might erupt now that Rubio is facing the prospect of a humiliating end to his campaign in his own home state.
Kasich next in Trump's warpath?
Trump's bullying often looks unhinged, but there's a kind of predictable ethics to it: If you're nice to him, you'll be the last to go. He refrained from targeting Dr. Ben Carson, for example, until Carson started leading polls in Iowa after which Trump compared him to a child molester.
If that pattern holds, Kasich could feel Trump's wrath next. In recent debates, Kasich has tried to stay above the fray and Trump has rewarded the governor's passive stance by letting him be. But a Fox News poll on Wednesday showed Kasich leading Ohio and other surveys show him behind but competitive with Trump.
In general, Kasich hasn't been the focus of many negative attacks mainly because he's never looked like a serious threat to win the nomination (he still doesn't). But with Trump, Rubio and Cruz now looking to squeeze every last vote out of the electorate before time runs out, all three of them have incentive to consider turning their attention to him.
This article originally appeared on MSNBC.com.