Here are five takeaways from Thursday’s debate.
Mr Trump stumbled on his past support for a national healthcare system but his most uncomfortable moment came when Ms Kelly challenged him on his views about women.
The subject of ISIS drew a hawkish response from Texas Sen.
The night just got stranger from there for The Donald, as he took a swipe at Rosie O’Donnell, bragged about forcing Hillary Clinton to attend his wedding and generally comported himself like a… well, like Donald Trump.
“He is already hedging his bet on the Clintons”, Paul said.
Later in the debate, former Florida Governor Jeb Bush, who is running second in polls, criticised Trump’s tone saying his “divisive” language could be detrimental to the Republican Party.
He also defended his remarks that Mexican “rapists” and criminals were crossing illegally into the US.
Paul and New Jersey Gov. Chris Christie engaged in a heated exchange over the USA Patriot Act and laws giving government access to Americans’ phone records.
Paul, a staunch opponent of the surveillance programs, said he wanted to collect more records from terrorists, not law-abiding Americans.
“If Hillary is the candidate, which I doubt, that would be a dream come true”, said neurosurgeon Ben Carson, the only black candidate in the field. He said Christie’s embrace of the counterterrorism policies amounted to “hugging” President Barack Obama, a reference to the governor’s embrace of the president in the aftermath of Superstorm Sandy in the days before the 2012 election.
“Yes, I’m sure it was”, said Trump.
The debate was hosted by Fox News Channel at Quicken Loans Arena in Cleveland, Ohio.
Kasich earned a rousing round of applause for his answer to a question about same-sex marriage.
“We got nothing and Iran gets everything they want”, said former Arkansas Gov. Mike Huckabee. Because you know what?
“I’m going to run hard, run with heart and run to win. But we need to control our border”, he said.
4. Marco Rubio is the real deal.
Asked whether God speaks to him, the Florida senator replied: “Well, first, let me say I think God has blessed us“.
It was a key test for Trump, whose unpredictable style and unformed policy positions mean he doesn’t fit neatly into any single wing of the Republican Party. “I spent all of last year with a lot of other conservatives pushing back effectively against the “War on Women”…It’s really disappointing when a front-runner gives the Democrats an ad and a talking point before he’s even in the ring”.
The two-term Ohio governor has often been known as much for his prickly demeanor and bluntness as much as his experience. “He had no specifics”, said a man who had supported Trump.
“What God calls us to do is follow his will”, he said. “And I hope people have seen that in my state”.
Trump entered the evening as the clear frontrunner among an extremely crowded field of 17 candidates – only 10 of which made it to stage.
Carly Fiorina, the former Hewlett-Packard chief, accused Trump of cosying up to the Clintons and slammed him for flip-flopping.