- The debate is at 9 p.m. Eastern from Milwaukee, Wisconsin
- The CNBC debate caused a near-rebellion among candidates unhappy with the questions from moderators
- Ben Carson and Marco Rubio have been the subject of new attacks in the media since the last debate
(CNN)And then there were eight.
For the first time this cycle, Tuesday's prime-time Republican debate in Milwaukee will feature just eight candidates from the unusually large field. Hosted by Fox Business and The Wall Street Journal, it comes as candidates are facing growing scrutiny from both their rivals and the media.
It's also the first time the contenders will be back together following last month's CNBC debate, which ended up with the candidates and Republican National Committee Chairman Reince Priebus attacking the network and moderators and a short-lived rebellion by the various campaigns.
Here are CNN's six things to watch:
Ben Carson under the microscope
Carson is getting a crash lesson on the scrutiny that comes with being a presidential frontrunner.
The political neophyte has confronted a series of questions about his past in recent weeks, as he's pulled slightly ahead of Trump in some polls.
Numerous networks and publications, including CNN, have examined and expressed skepticism about aspects of Carson's biography, including stories of Carson's violent outbursts as a youth; a "scholarship" the retired neurosurgeon claims to have been offered from West Point; and his alleged role sheltering fellow students during a race riot in high school.
So far, Carson has responded with sharp indignation, slinging choice words like "stupid" and "sick" at the media.
The 64-year-old has also said it isn't his responsibility to "corroborate everything I have ever talked about in my life." But questions about his biography will likely continue dog the candidate until he can do precisely that -- and Tuesday's debate will provide that opportunity.
How will Rubio defend himself?
Rubio is the candidate to watch these days. His poll numbers are on the rise, he's picking up key endorsements, and he's had several strong debate performances -- all while his one time mentor, Jeb Bush, is struggling to turn around a flailing campaign.
But being on the upswing also means Rubio is increasingly finding himself a tempting target.
On Tuesday, the Florida senator could get hit on a range of issues including his use of a Florida Republican Party charge card; his stance on immigration reform; management of his personal finances; and his attendance record in the Senate.
In previous debates, Rubio's demonstrated that he's nimble at fending off attacks. When Bush slammed the senator for missing votes in Congress at last month's GOP debate in Boulder, Rubio fired back, suggesting the former Florida governor was simply listening to political advisers who wanted to attack him.
Rubio spokesman Alex Conant struck an optimistic tone this week and said the senator's focus would remain unchanged heading into Tuesday night.
"We feel good about tomorrow's debate," Conant told CNN. "Marco is going to do the same thing that he did in the first three debates: talk about his positive agenda for a new American century."
Jeb Bush's latest reboot
Bush's debate performances have been so lackluster this cycle that he's enlisted professional help.
Describing the advice he's received from his newly hired media coach, Bush said earlier this month: "He's telling me to be me. He's telling me to own what I believe."
But the precise dilemma for Bush when he walks onto Tuesday's prime time stage is whether he's better off being himself -- the former Florida governor is a self-described introvert and uncomfortable in the role of attack dog -- or trying to show that he can be an aggressive and combative candidate.
If Bush is preparing to deliver any zingers in Milwaukee, he'll also need go the extra mile to ensure that the strategy doesn't backfire.
In last month's GOP debate in Boulder, Bush went after Rubio for his poor attendance record in the Senate, only to have Rubio swing back and get the last word in the testy exchange and saw some supporters lament the plan of attack in the first place.
Is Donald Trump so yesterday?
Donald Trump rose to the top of the polls as a political sensation, shocking both voters and the media with his unorthodox campaign and unfiltered rhetoric.
But that novelty may be starting to wear thin.
After riding high in the polls for months, the New York businessman has lost his first-place standing -- both nationally and in states like Iowa -- to Carson. If his larger-than-life personality helped draw record audiences to the first few debates, those ratings have also started to fall.
And over the weekend, Trump's highly anticipated appearance on NBC's "Saturday Night Live" was widely panned. His jokes fell flat and his routine felt, well, boring.
Chris Christie at the kids' table
For the first time, Chris Christie will get to stand in the middle of the debate stage Tuesday.
Unfortunately, that moment will be at the "undercard" debate.
The New Jersey governor was bumped off of the prime time debate, relegated to an earlier event featuring three other lower tier Republicans: Mike Huckabee, Rick Santorum and Bobby Jindal.
Not long ago, the famously brash governor was considered one of the Republican Party's most promising rising stars. But the New Jersey ethics scandal dubbed "Bridgegate" seems to have permanently scarred Christie's political ambitions, leaving him languishing in the single digits nationally.
If there's a silver lining, it's that Christie has a better chance of standing out and dominating the discussion in a crowd of just four.
"I've said since the beginning that it doesn't matter what debate stage I'm on," Christie said in a fundraising email this week. "Give me a podium and I'll be there, anytime, anywhere."
Moderators in the spotlight
It's not just the candidates that will feel the heat Tuesday — there's also a lot riding for the moderators.
CNBC, the host of the last GOP debate in Boulder, Colorado, found itself on the receiving end of a litany of hostile criticism. Candidate after candidate slammed the network for dishing out "gotcha" questions and being more concerned about trying to put on a good show than drawing out substance.
The reviews were so brutal that the candidates collectively called for change, arguing that the individual campaigns needed more of a say in determining — and agreeing to -- the format of future debates.
The Fox Business and Wall Street Journal moderators hosting Tuesday's event are likely to be sensitive to the concerns raised last month and aware that any line of questioning perceived as being in poor taste could once again draw fierce blow back.
Too much public whining, however, could also work against the candidates.
"It turns out they can't handle a bunch of CNBC moderators at the debate," President Barack Obama said after last month's debate. "Let me tell you, if you can't handle those guys, then I don't think the Chinese and the Russians are going to be too worried about you."