5 Things to Watch for at Tonight's Republican Debate

— -- The do-or-die debate has arrived.

With must-win, winner-take-all contests in Florida and Ohio just days away, time is running short for anti-Trump candidates to make their move to hold back the real estate mogul in the delegate count.

Recent polling in Ohio shows a close race between Donald Trump and Gov. John Kasich, while Florida polls show Marco Rubio trailing by as many as 20 percentage points in his home state.

With so much on the line, here are five things to watch for at tonight’s GOP debate held at the University of Miami in Florida:

A New Trump?

Trump struck an unusual chord in Tuesday’s primary night press conference. Despite feeling like an infomercial at times, Trump’s press conference in Jupiter, Florida, was what some pundits called more “presidential” than what we’ve seen from the GOP front-runner.

“I'm a unifier. I get along with people. I have great relations,” Trump boasted, saying later, "I say, let’s come together folks, we’re gonna win.”

Could tonight’s debate see a similar Trump?

Rubio Hanging By a Thread

Tonight’s debate is on Rubio’s home turf, where he desperately needs to win or else his campaign is finito.

Some might argue it already is and that’s why Rubio needs to generate a memorable moment that could make a difference in Florida next Tuesday.

He's expected to mostly keep up his attacks on Trump’s policies, since it’s too late to back down.

Cruz Prepares to Fight Alone

Ted Cruz solidified his second place in the GOP race Tuesday, with a seventh state under his belt. Now, he must prepare for the possibility of a one-on-one race with Trump.

In a town hall with MSNBC, Rubio admitted he’s “not entirely proud” of his personal attacks on Trump, and Kasich shies away from personal attacks. So Cruz could be on his own tonight when it comes to taking on Trump, and that could be a preview of the race to come.

Can Cruz handle the heat? Tonight could be telltale.

Kasich Keeping His Cool

The Ohio governor didn’t get the boost he needed out of his third-place, double-digit loss in Michigan -- so now all of his chips are on Ohio.

Kasich himself admits he doesn’t have a path to the nomination outright: Even after winning Ohio, he would need 85 percent of the remaining delegates to win the nomination. So he’s hoping for a contested convention.

Kasich’s debate strategy so far has been to remain above the fray and focus on a positive message -- part of the reason he’s so popular in his home state. Recent polling in Ohio has shown a tight race between him and Trump.

Issues That Might Come Up

Here are a few things that might come up tonight: The alleged incident where Trump’s campaign manager roughed up a Breitbart reporter, Rubio’s regret over personal attacks against Trump, and whether it’s time for a candidate to drop out.

Also, since Hispanics make up nearly 24 percent of the population in the Sunshine State, immigration is expected to be a topic of discussion, as well Trump’s “beautiful tall wall,” as Democratic front-runner Hillary Clinton has described it.

The CNN Republican debate begins at 8:30 p.m. ET.