Donald Trump has said he will be backing out of the last Republican debate before the Iowa caucuses.
The decision was announced on Tuesday evening by Mr Trump’s campaign manager - just 48 hours before the Fox News debate.
Mr Trump’s campaign released a statement saying: “Unlike the very stupid, highly incompetent people running our country, Mr Trump knows when to walk away. Fox News think they can toy with him, but Mr Trump doesn’t play games.”
The statement says Mr Trump will instead host an event in Iowa to raise money for “the Veterans and Wounded Warriors”.
The announcement followed a press conference in which Mr Trump dismissed Fox News' debate moderator, Megyn Kelly, as a "lightweight", “third-rate reporter” and claimed she had been “toying” with him.
On Tuesday night’s airing of Ms Kelly’s Fox News show, The Kelly File, the host said the debate would go on “with or without Mr Trump”.
A Fox News spokesperson said Mr Trump was still welcome to participate in the debate but would not be allowed to “dictate the moderators or the questions”.
So, who is the woman Donald Trump is running scared of?
A journalist and political commentator, Ms Kelly has received criticism from Mr Trump since moderating the first GOP debate in August, when she quizzed him about past comments he made about women.
The host of The Kelly File, currently the second most-watched programme in all of the US’s cable news, made headlines and received praise for her tough questioning.
“You’ve called women you don’t like fat pigs, dogs, slobs and disgusting animals,” Ms Kelly told the Republican frontrunner.
She also queried Mr Trump’s party affiliation, asking: “When did you actually become a Republican?”
In an interview with CNN after the debate, Mr Trump criticised Ms Kelly’s approach, saying she had “had blood coming out of her eyes, blood coming out of her wherever” while questioning him.
Mr Trump has since repeatedly criticised Ms Kelly and the jibes have intensified in the run-up to Thursday’s debate.
Fox News has even accused Mr Trump’s team of threatening her.
On Saturday, campaign manager Corey Lewandowski reportedly said Ms Kelly had a "rough couple of days after that last debate" and he "would hate to have her go through that again."
Fox News said in a statement: “It should be clear to the American public by now that this is rooted in one thing – Megyn Kelly, whom he has viciously attacked since August and has now spent four days demanding be removed from the debate stage.
"Capitulating to politicians’ ultimatums about a debate moderator violates all journalistic standards, as do threats, including the one levelled by Trump’s campaign manager Corey Lewandowski toward Megyn Kelly."
Donald Trump's most controversial quotes
Donald Trump's most controversial quotes
1/14 On Isis:
"Some of the candidates, they went in and didn’t know the air conditioner didn’t work and sweated like dogs, and they didn’t know the room was too big because they didn’t have anybody there. How are they going to beat ISIS?"
2/14 On immigration:
"I will build a great wall — and nobody builds walls better than me, believe me —and I’ll build them very inexpensively. I will build a great, great wall on our southern border, and I will make Mexico pay for that wall. Mark my words."
3/14 On Free Trade:
"Free trade is terrible. Free trade can be wonderful if you have smart people. But we have stupid people."
PAUL J. RICHARDS | AFP | Getty Images
4/14 On Mexicans:
"When Mexico sends its people, they’re not sending their best. They’re sending people that have lots of problems. They’re bringing drugs. They’re bringing crime. They’re rapists."
5/14 On China:
"I just sold an apartment for $15 million to somebody from China. Am I supposed to dislike them?... I love China. The biggest bank in the world is from China. You know where their United States headquarters is located? In this building, in Trump Tower."
6/14 On work:
"If you're interested in 'balancing' work and pleasure, stop trying to balance them. Instead make your work more pleasurable."
7/14 On success:
"What separates the winners from the losers is how a person reacts to each new twist of fate."
8/14 On life:
"Everything in life is luck."
9/14 On ambition:
"You have to think anyway, so why not think big?"
10/14 On his opponents:
"Bush is totally in favour of Common Core. I don't see how he can possibly get the nomination. He's weak on immigration. He's in favour of Common Core. How the hell can you vote for this guy? You just can't do it."
11/14 On Obamacare:
"You have to be hit by a tractor, literally, a tractor, to use it, because the deductibles are so high. It's virtually useless. And remember the $5 billion web site?... I have so many web sites, I have them all over the place. I hire people, they do a web site. It costs me $3."
12/14 On Barack Obama:
"Obama is going to be out playing golf. He might be on one of my courses. I would invite him. I have the best courses in the world. I have one right next to the White House."
13/14 On himself:
"Love him or hate him, Trump is a man who is certain about what he wants and sets out to get it, no holds barred. Women find his power almost as much of a turn-on as his money."
14/14 On America:
"The American Dream is dead. But if I get elected president I will bring it back bigger and better and stronger than ever before and we will make America great again."
Mr Trump has previously said he would not participate in the event because of Fox's insistence on including Ms Kelly.
"Megyn Kelly shouldn't be in the debate," Mr Trump said at a press conference before a campaign event in Iowa. "I'm not a fan of Megyn Kelly. I think she's a third-rate reporter. I think she is frankly not good at what she does. And I think they could do a lot better than Megyn Kelly".
Fox News Chairman, Roger Ailes, defended Ms Kelly telling The Washington Post: “Megyn Kelly is an excellent journalist, and the entire network stands behind her. She will absolutely be on the debate stage on Thursday night."
Additional reporting by Press Association