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Things to watch at GOP debate

(CNN) -- Donald Trump loves the spotlight and the camera.

But when he takes center stage Thursday night, it won't be as the star of a reality TV show -- it will be as the Republican Party's front-runner presidential candidate.

Trump and nine of his GOP rivals will battle it out in the 2016 cycle's inaugural GOP primary debate, hosted by Fox News in Cleveland. The stakes are high, as each participant clamors to stand out from a nearly unprecedented pack of 17 declared GOP candidates.

But the pressure is perhaps the greatest for Trump, whose coveted position center stage on Thursday marks his remarkable rise to the top of the national polls. With an unorthodox campaign style and at times inflammatory remarks, the real estate magnate has dominated the early 2016 media coverage and upended the GOP primary.

Trump's performance will dominate the headlines, but h ere are six things to watch heading into debate night:

Can Bush avoid stumbles?

Fourteen GOP candidates got a taste of what's to come on the debate stage during a forum in New Hampshire on Tuesday night.

And it did not bode well for Jeb Bush.

As he addressed a range of issues from education policy to the threat of ISIS, the former Florida governor appeared visibly nervous and flustered, more than once tripping over his words. The most uncomfortable moment came during Bush's last few minutes in the chair, when he was asked about the two ex-presidents in his family.

\"My dad is probably the most perfect man alive so it's pretty hard for me to be critical of him,\" Bush began.

Then: \"In fact I got a T-shirt that says, uh, at the Jeb swag store, that says, I'm the, uh, I'm, I'm the, 'My dad's the great man alive. If you don't like it, I'll take you outside.\"

Beltway reporters and pundits expressed a mix of surprise and dismay at Bush's fumbled performance, particularly given his earlier struggles to discuss issues related to his family. It also revived fresh questions about whether Bush, who left the governor's office in 2007, has been out of practice for too long.

He ran into trouble again on Wednesday when, during a riff against Planned Parenthood, he said, \"I'm not sure we need half a billion dollars for women's health issues.\"

Hillary Clinton, the presumed Democratic presidential front-runner, hit back hard over Twitter and Bush later walked back his statement, saying he \"misspoke.\"

\"I was referring to the hard-to-fathom $500 million in federal funding that goes to Planned Parenthood -- an organization that was callously participating in the unthinkable practice of selling fetal organs,\" he said.

A solid performance on Thursday is particularly critical for Bush as he attempts to maintain his second-place standing in national polls.

Will anyone in the middle tier break out?

Here's the near universal challenge for the GOP candidates whose last name isn't Trump: How to stand out?

All of the Republican candidates with the exception of Bush and Scott Walker, who have broken into double digits in some recent polls, have struggled to catapult out of the very crowded middle-tier pack. A stellar debate performance this week -- along with some favorable headlines -- could be the boost some contenders need to catch up to their top-tier rivals.

The candidates on stage Thursday night whose poll numbers have been around the low- to mid-single digits include New Jersey Gov. Chris Christie, Ohio Gov. John Kasich, Florida Sen. Marco Rubio, Kentucky Sen. Rand Paul, former Arkansas Gov. Mike Huckabee, Texas Sen. Ted Cruz and neurosurgeon Ben Carson.

Former GOP presidential candidate and Utah Gov. Jon Huntsman said the the first debate is a ripe opportunity for the governors on stage to make a splash.

\"We're looking for problem solvers, we're looking for solutions to the basics like jobs and a balanced budget and entitlements,\" Huntsman said on CNN Tuesday. \"And that's clearly an area where a governor can really differentiate himself from the rest of the pack.\"

Kasich, in particular, is an interesting candidate to watch.

He launched his campaign mid-July and his poll numbers ticked up recently, giving a last-minute boost to qualify him for the first debate. Kasich's allies view his record of fiscal conservatism as key to appealing to a broader electorate.

Don't forget the 5 p.m. debaters

The earlier debate will include Rick Perry, Rick Santorum, Bobby Jindal, Carly Fiorina, Lindsey Graham, George Pataki and Jim Gilmore.

This smaller group is at the very bottom of the polls for now.

While the late-afternoon event will draw a much smaller audience than its prime-time counterpart, it will nevertheless show early signs of who in the group has the potential to shine later in the cycle.

\"The people in the five o'clock debate should go into that debate with the idea that if they have the right performance, the next time around, they're going to be in the 9 o'clock debate,\" Newt Gingrich, the former House speaker and Republican presidential candidate, told CNN. \"And you'll have several people in the 9 o'clock debate collapsing as serious candidates in the next few months. Both are true.\"

The moderators

Three Fox News anchors will guide the candidates through two hours of grilling on Thursday night: Bret Baier, Megyn Kelly and Chris Wallace.

It will be the role of those moderators to facilitate a fair and engaging discussion. A few things to keep an eye out for:

-- Three moderators, different styles? Baier, Kelly and Wallace each host a show on Fox and have varying interviewing styles. Will one emerge as the good cop, and another as the bad cop?

-- Who gets the toughest treatment? The moderators will push for details and clarity and call out obvious contradictions. Pushing a candidate extra hard in one policy area -- Trump on immigration or Bush on Common Core, for example -- could be a telling sign of those candidates' perceived vulnerabilities.

-- Do the moderators strictly enforce the timer? Every second at the debate is precious, and it's incumbent on the moderators to keep everyone in line. More time means more opportunities for a candidate to promote their platform and go after a rival candidate.

The invisible candidate on stage: Hillary Clinton

Expect to hear plenty of Clinton-bashing.

The ultimate prize for the GOP candidates is not only to clinch the party's nomination, but to one day face off against the former secretary of state in a general election -- and defeat her. The appeal that each of the Republican candidates has to make to voters, in other words, is not only that they're the best within the GOP field, but that they're also the best option for beating Clinton.

\"Here's the thing. In order to beat Hillary Clinton, or whoever their nominee turns out to be, we have to have a nominee on our side who is going to throw every punch because this is a fight,\" Carly Fiorina, the former Hewlett-Packard CEO who will participate in the 5 p.m. debate, said earlier this week in New Hampshire.

There's a long list of grievances from which to choose.

Clinton has been dogged by a series of scandals and accusations, ranging from the her use of a personal email server at the State Department to her handling of a deadly attack on the U.S. consulate in Benghazi, Libya, to the massive personal wealth that she and her husband, Bill Clinton, have amassed since he left the White House.

'Oops'

It was one of the most memorable gaffes of the 2012 election and a moment that all of the candidates on stage Thursday will try to avoid.

At a GOP primary debate hosted by CNBC in November 2011, former Texas Gov. Rick Perry vowed to shutter three government agencies as president.

But after naming the Commerce Department and Education Department, Perry lapsed into a momentary brain freeze. For an agonizing 45 seconds, Perry struggled in search of the third agency. Pressed by the moderator, Perry finally conceded: \"I can't. Oops.\"

It's not that one gaffe could single-handedly tank someone's candidacy. But a bad stumble, particularly in the age of ubiquitous YouTube videos, Vines and GIFs, could follow a candidate around for months and make it frustratingly difficult for them to refocus.

\"There were a couple of debates where after the debate, you just knew that the candidate wasn't going to be there anymore,\" said Gingrich. \"I always tell people: the thing about the debate is not that you may win, but that you may lose.\"

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