Front-runners Donald Trump and Ted Cruz are expected to clash, breaking their months-long entente in the last Republican presidential debate of 2015, BBC reports. It is the first Republican debate since Mr Trump urged the US impose a ban on Muslim arrivals, in light of the California terror attacks.
The plan was condemned by his White House rivals and several world leaders. New York billionaire Mr Trump is the frontrunner but Texas Senator Ted Cruz has surged in recent weeks. Tensions have recently increased between the two men who have made pains to avoid criticising each other.
National security is expected to be a central theme of the night, two weeks after a radicalised Muslim couple killed 14 people in California, and just over a month since the attacks in Paris. One of the suspects in the California attack, Tashfeen Malik, professed support for Islamic State militants on social media.
The attack in Paris brought the issue of Syrian refugees to the front of the US political debate. That debate expanded to include the entry of all Muslims to the US with Mr Trump’s proposed ban following the attacks in California. Mr Trump loomed large over the so-called undercard debate, with the four candidates split over the efficacy of his proposed ban.
Senator Lindsey Graham apologised to US-allied Muslim leaders saying: “I am sorry. He does not represent us”. However, it was the threat of the so-called Islamic State (IS) that dominated the first debate. The candidates argued at-length over whether US troops should be sent to Syria and Iraq to engage in direct combat with IS militants.
Mr Graham led the rhetorical charge into battle, while former Arkansas Governor Mike Huckabee said US troops were exhausted after the wars in Iraq and Afghanistan. After Mr Trump’s proposal generated global criticism, Mr Cruz has tried to cast himself as a more electable alternative.
Meanwhile, Florida Senator Marco Rubio will be working to pitch himself as the favoured alternative to both men in the main debate – capable of capturing both the Republican establishment voters and those who crave a so-called “outsider”.
The debate will also prove crucial for two candidates who have so far struggling in the polls: Florida Governor Jeb Bush and New Jersey Governor Chris Christie.
Mr Bush, whose campaign is flush with cash but strained when it comes to support, is looking to head off calls that he should drop out of the race; those calls have been growing louder in recent weeks.
Mr Christie did not enjoy early support, but appears to be gaining ground as the other governor loses it. In the important primary state of New Hampshire, he’s captured important endorsements and appears to be gaining in polls in recent weeks.
Also on the stage, will be Ben Carson, who is struggling to regain his footing after a series of missteps on foreign policy issues.
The main debate featuring the top eight Republican candidates will start at 2100e (0200 GMT), after a so-called undercard debate featuring those in the lower ranks.
The state-by-state primary contests in the presidential election begin in six weeks in Iowa on 1 February and will last for months. Each party will formally nominate their candidate over the summer, with Hillary Clinton the favourite to win the Democratic nomination.
Americans will finally go to the polls in November, and the newly elected president will assume office in late January of 2017.