The first GOP debate is tonight! Here's what you need to know

So three governors, two former governors, three Senators, a retired neurosurgeon, and a real-estate magnate walk onto a stage...

The first Republican presidential primary debate will take place Thursday night, as the top 10 - and bottom seven - Republican candidates will look to stand out amid a crowded field and the behemoth that is front-runner Donald Trump.

Fox News, which is hosting the first debate, has limited the Republican participants in the prime-time debate to the 10 candidates polling best in an average of five recent national polls.

The candidates who don't make the prime-time debate stage will participate in a separate debate at 5 p.m. ET, hours before the primetime, 9 p.m. ET showdown.

The polling

According to Real Clear Politics' average of five recent national polls, here's a look at where the candidates stand going into Thursday night. From the top tier:

• Donald Trump, real-estate magnate: 24.3% average as of Thursday
• Jeb Bush, former Florida governor: 12.5%
• Scott Walker, Wisconsin governor: 9.5%
• Mike Huckabee, former Arkansas governor: 6.8%
• Ben Carson, retired neurosurgeon: 5.8%
• Ted Cruz, US senator from Texas: 5.5%
• Marco Rubio, US senator from Florida: 5.3%
• Rand Paul, US senator from Kentucky: 4.5%
• Chris Christie, New Jersey governor: 3.5%
• John Kasich, Ohio governor: 2.8%

And the bottom tier:

• Rick Perry, former Texas governor: 1.8%
• Bobby Jindal, Louisiana governor: 1.5%
• Rick Santorum, former US senator from Pennsylvania: 1.3%
• Carly Fiorina, former Hewlett Packard CEO: 1.3%
• Lindsey Graham, US senator from South Carolina: 0.5%
• George Pataki, former New York governor: N/A
• Jim Gilmore, former Virginia governor: N/A

Who needs a big night

It's an important night for all candidates, as it'll be the first time many Americans tune into the still-nascent presidential campaign.

But the night will be especially important for Trump, who has become the overwhelming front-runner in the GOP race since he launched his campaign in mid-June. A good performance in Cleveland would continue a streak of seriousness in the campaign that wasn't seen early on. A bad performance could lead to more calls that the flame-out will happen sooner rather than later.

"His stamina and momentum have surprised us," said Chris Krueger, a political strategist at Guggenheim Securities. "Some interesting data points from the latest Fox poll: in their poll two months ago, 59% of Republicans said they would NEVER support Trump. Only 33% say that in this poll."

It'll also be an important campaign moment for those with momentum - like Kasich, whose poll numbers have gone from virtually zero to in the top 10 since his campaign launch on July 21. And the candidates who have lost momentum amid the Trump surge - Rubio, Christie, Paul, and more - will look for a moment to turn it around.

From Guggenheim's Securities' Krueger, here's a look at what each candidate needs to do:

Donald Trump. We still see almost no chance that Trump is the nominee, though his stamina and momentum have surprised us. Some interesting data points from the latest Fox poll: in their poll two months ago, 59 percent of Republicans said they would NEVER support Trump. Only 33 percent say that in this poll. Trump is the top vote getter among both men (29%) and women (24%). And he currently leads among both self-identified tea partiers and evangelical Christians.

Jeb Bush. We would expect most of Trump's fire to be directed against Bush and it is very unclear how he will respond. If Jeb can get through the debate by defining his candidacy with some solid sound bites, he will not lose the debate, but given his recent polling slide he could really use a win. Jeb needs a host of lock-down answers to keep his critics on the stage at bay (recent Planned Parenthood remarks, Common Core support, immigration reform support, time at Lehman/Barclays, last name, etc.).

Scott Walker. Just like Rubio - playing the long game and wins by not losing. Walker has already defined his campaign well, though will need help defending his lack of experience in foreign policy, lack of a college degree, and the perception of policy flip flops.

Mike Huckabee. Huckabee had one of the great lines from 2008 (in our opinion): I'm a conservative but I'm not angry about it. Unclear if that Huckabee shows up, or the angrier one from the past few months.

Ben Carson. Carson is very popular with the base and is likely to play the genial adult on the stage and could well have the sound bite of the night.

Ted Cruz. Cruz will probably be the only candidate openly praising Trump, proclaim that he will not attack any Republicans, and then will launch into a broadside against another Republican not named Trump.

Marco Rubio. Rubio is playing the long game and wins by not losing, though he needs to define his campaign and to explain to Republicans why he is not a conservative, Cuban version of Obama (young Senator with little experience who is a dynamic speaker with a unique life story).

Rand Paul. The Paul campaign's failure to launch has been (in our opinion) one of the biggest surprises in 2016. Paul has very few allies on the stage and could well become a punching bag.

Chris Christie. Christie is one of the few candidates talking about entitlement reform, which we would expect to hear about in the debate. The question is whether he trains his fire on Rand Paul on national security and drug legalization or perhaps creates a moment by going head-to-head against Bush.

John Kasich. Expect Kasich to attempt to be the grown-up in the debate, attempt to keep his legendary temper in check, and to focus on his record in Ohio. Kasich also is likely to bring up his general election strengths.

The issues to watch for

Greg Valliere, the chief political strategist at the Potomac Research Group, looks at what issues could come up during the 1.5-hour debate:

• Will anyone offer specific proposals to jump-start the economy?

• Who will have the guts to talk about trimming entitlements?

• Will China-bashing be a highlight of the the debate?

• Will the Federal Reserve be in the cross-hairs, as usual?

• Will anyone get specific on tax reform?

• Does anyone care about the deficit any more?

• Crony capitalism - a sleeper issue; has Big Business become a pariah?

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