Florida Governor Ron DeSantis will face off against former UN ambassador Nikki Haley in the last Republican debate before the Iowa caucus next week.
The debate in Des Moines comes as both candidates lag far behind former President Donald Trump in the polls.
The 15 January caucus will be the candidates' first electoral test in their effort to become the Republican presidential nominee in 2024.
Mr Trump will not be in the debate, but will appear in a Fox News town hall.
The former president has so far boycotted every Republican debate, a strategy that proved fruitful. He holds commanding poll leads in Iowa, sometimes up to 30 points, ahead of the state's caucuses.
The CNN debate - which is slated for 21:00 EST (02:00 GMT) - offers Mr DeSantis and Ms Haley, who stand in second and third place at the polls respectively, a final opportunity to make their case to caucus goers ahead of next week.
Two other candidates, entrepreneur Vivek Ramaswamy and New Jersey Governor Chris Christie, failed to qualify.
The hours before the debate saw last-minute sparring between the two candidates over the airwaves, with a pro-Haley ad criticising Mr DeSantis for allegedly mischaracterising her comments on Gaza, immigration and Hillary Clinton. The ad was entitled "DeSantis is lying because he's losing".
A super PAC that supports Mr DeSantis also released an ad in Iowa which attacked Ms Haley for saying that the upcoming New Hampshire primary - the second Republican contest - would "correct" the results of Iowa.
"Nikkie Haley told New Hampshire what she really thinks about Iowa," the narrator says in the video.
Mrs Haley was recently buoyed by fresh polling that suggests she has cut Mr Trump's lead in New Hampshire to single digits. Analysts have said a strong showing there could make her Republican party's prime alternative pick to the former president.
Since serving as Mr Trump's ambassador to the UN during his time in the White House, she has broken with her one-time boss on key areas of foreign policy and criticised his willingness to do business with China.
She has seemed to promise a return to a more traditional Republican party, embracing a hawkish foreign policy and faulting members of both parties, including Mr Trump, for running up the national debt.
A former South Carolina governor, Mrs Haley has also argued that she is a more palatable candidate for undecided voters than Mr Trump.
"The only way we're going to win the majority of Americans is if we go forward with a new generational leader that leaves the negativity and the baggage in the past and goes forward with the solutions for the future," she told a town hall meeting in Iowa on Tuesday.
But as her star has ascended in recent weeks, she has faced increased attacks from Mr Trump and Mr DeSantis.
She also suffered a recent gaffe, as she failed to say that the Civil War was fought over the issue of slavery - which attracted criticism.
Watch: Haley leaves out slavery as a cause of US Civil War
By contrast, Mr DeSantis, the two term Florida governor, has sought to tack hard to Mr Trump's right.
He has fought a campaign based broadly on culture wars issues and has touted his record of tackling what he called "woke" policies in his home state.
While an early favourite as an alternative choice to Mr Trump, he has struggled to differentiate himself from his one-time ally. The former president raised Mr DeSantis from relative obscurity as a member of Congress and endorsed him in his run for the Florida governor's office in 2017.
Bob Van Der Plaats - the leader of the influential Family Leader organisation - sought to assure Iowa voters that it was safe to support Mr DeSantis over Mr Trump in a Des Moines Register op-ed on Wednesday.
"Caucusing for Ron DeSantis is a good way to be a friend to Donald Trump," Mr Van Der Plaats wrote.
He added that a "DeSantis presidency ensures justice for Trump" and that his preferred candidate is better equipped to fight government "bureaucracy" than the former president.
It does appear Mr DeSantis is better suited to perform well in Iowa than Mrs Haley, where evangelical voters - a key voting block in the state - could be attracted to his staunch conservative values.
Nevertheless, both candidates will likely have to exceed expectations to some degree to step out from under Mr Trump's looming shadow and keep their campaigns alive.
Related Topics
-
- 11 December 2023
-
- 21 November 2023
-
- 2 January
