Eight White House hopefuls prepared Tuesday to do battle in the latest Republican presidential debate, with surging outsider Ben Carson's tumultuous backstory under the microscope and Jeb Bush fighting for his political life.
The showdown in Milwaukee, Wisconsin comes two and a half months before the first state-wide votes in the primary process to determine which Republican and which Democrat will square off in the November 2016 contest to succeed Barack Obama.
Republicans Carson and billionaire Donald Trump are riding high in the polls, outshining their establishment counterparts, most of whom are struggling to gain traction in a political environment saturated with populist anger.
Carson, a retired neurosurgeon who like Trump has never held elected office, has come under intense scrutiny as US media pore over elements of his undeniably inspirational personal narrative, including his own accounts of his violent adolescence, when he says he attempted to kill a classmate.
"There's no question I'm getting special scrutiny, because there are a lot of people who are very threatened, and then they have seen the recent head-to-head polling against Hillary (Clinton) and how well I do," Carson told CBS television on Sunday.
Carson, who has also been challenged over his tale of being offered a prestigious military scholarship, has a chance to shake things up after a week of bad press, Republican strategist David Payne said.
"If he goes into the debate talking about ObamaCare and other health care issues, he can own the stage," Payne, of Vox Global, told FoxNews.com. "He can show a lot of energy because he knows this topic."
Many will be watching whether Jeb Bush, the politically privileged early frontrunner now languishing in single-digit support, will show more spark in the fourth Republican showdown than he did in the third, when he was bested by Senator Marco Rubio, his former political apprentice.
"I know I have to get better," Bush told supporters last week after his lackluster performance.
Amid pressure to narrow the field for the party's fourth debate -- the race two months ago had bulged to 17 contenders -- broadcaster Fox Business Network changed the format from previous Republican clashes, with only eight candidates at the podiums instead of 10.
Low-pollers New Jersey Governor Chris Christie and former Arkansas governor Mike Huckabee failed to make the cut. They are relegated to the undercard debate, which begins at 0000 GMT Wednesday and features four back-of-the-pack candidates.
Two others, Senator Lindsey Graham and former New York governor George Pataki, have generated virtually zero support and were bumped from the proceedings altogether.
The main event kicks off at 0200 GMT Wednesday.
The previous debate, hosted by cable business channel CNBC, is remembered for the confrontational tone that moderators took with the candidates, many of whom complained bout being asked "gotcha" questions.
Republican National Committee Chairman Reince Priebus, who labeled the debate a "crap sandwich," said he hoped Tuesday night would be an opportunity to turn the page and address substantive issues.
Fox Business Network has vowed to play nice. "My goal is to make myself invisible," Neil Cavuto, one of three moderators for the prime-time event, told Politico.
"We're not the issue," he stressed. "The answers to what we're raising become the issue."
Republicans have been in an adversarial relationship with debate moderators for decades, said Ben Voth, a communications professor at Southern Methodist University.
"Ever since 1992, the Republicans have pretty consistently taken the view that the media is hostile and unfair to their arguments," he told AFP.
Trump, whose confrontational bluster has been a hallmark of his campaign, said he is ready for whatever comes his way.
"I think it will be very fair questions, unlike the catastrophe of the last" debate, he told ABC's "This Week."
The real estate mogul also hinted at one line of attack on the economy -- a focus of Tuesday's debate -- releasing a policy paper targeting China over its currency, which many economists say Beijing deliberately undervalues to boost exports.
"On day one of the Trump administration, the US Treasury Department will designate China as a currency manipulator," the paper reads, according to ABC.
"We're losing $400 billion a year with China in terms of imbalance," Trump told the network. "They're killing us."