Donald Trump will be at center stage later as 10 leading Republican presidential candidates look for a break-out moment at their first debate on the road to the November 2016 US election.
The real estate mogul, along with rivals Jeb Bush, Scott Walker, Marco Rubio and six others, square off at 2am Irish time at Quicken Loans Arena in Cleveland, Ohio, just three hours after seven candidates who rank lower in the polls wrap up a separate debate.
The first debate includes former Texas governor Rick Perry, former US Senator Rick Santorum and five others in the crowded 2016 Republican field.
Fox News invited the top 10 candidates in an average of five recent opinion polls. Fox's decision to limit the participants created weeks of anxiety for those on the bubble.
It also was criticised by some Republicans as unfair given the number of candidates bunched in the low single digits, well within the margin of error of most polls.
The prime-time event, to be moderated by Fox News anchors Bret Baier, Megyn Kelly and Chris Wallace, will offer Americans their first look at the major Republican candidates en masse six months before Iowa holds the first nominating contest.
For Mr Trump, the first debate offers an opportunity to prove whether he has a substantive vision for the country and go beyond brick-throwing rhetoric.
His rapid rise to the top of the Republican pack in polls has earned him center-stage status in the debate.
Mr Trump's take-no-prisoners style of campaigning, with a penchant for incendiary remarks such as those on the war record of Senator John McCain and on Mexican immigrants, whom he branded as criminals and rapists, has also earned him a level of press coverage that has eclipsed many of his rivals.
Leading contenders like Mr Bush, Mr Walker and Mr Rubio are likely to stress their records and vision while others more in need of a polls boost like Ohio Governor John Kasich or New Jersey Governor Chris Christie may find value in tangling with Mr Trump.
The Bush camp made clear the former Florida governor intends at the debate to sell his record as a conservative, tax-cutting governor. The Walker camp made similar pledges about the Wisconsin governor's aim.
Republican strategist Katie Packer said the smart strategy is to steer clear of the mud-slinging Mr Trump.
"There's no point in fighting with a pig because you just get dirty and you make the pig mad," she said.
