“I can totally make that pledge if I’m the nominee,” he said when Fox News host Bret Baier asked candidates whether they would promise to support whoever clinches the nomination.
But, “I will not make the pledge at this time,” Trump said, as the audience booed.
The real estate mogul instead reserved the right to run as a third-party candidate.
Though he said he can “fully understand” the ramifications –- a third-party candidacy would possibly give Democrats the edge -– he refused to grant his competitors that "leverage."
“I want to win as the Republican," he said. "I want to run as the Republican nominee."
That's when rival candidate Sen. Rand Paul chimed in.
"This is what's wrong. He buys and sells politicians of all stripes!" the Kentucky senator said. "He's already hedging his bet on the Clintons. Okay? If he doesn't run as an Republican, maybe he supports Clinton or maybe he runs as an independent. But I tell you, he's already hedging his bets because he's used to buying politicians."
"I've given you plenty of money," Trump fired back.
Later in the debate, Fox News anchor Megyn Kelly confronted Trump about his rhetoric.
“You’ve called women you don’t like fat pigs, dogs, slobs, and disgusting animals,” Kelly began. “Your Twitter account --”
“Only Rosie O’Donnell,” Trump interrupted.
(Trump has long nursed a grudge against the talk show host, making derogatory comments about her.)
“For the record, it was well beyond Rosie O’Donnell,” Kelly clarified.
“Your Twitter account has several disparaging comments about women's looks,” she continued. “You once told a contestant that it would be a pretty picture to see her on her knees. Does that sound like the temperament of a man we should elect as president?”
“I think the big problem this country has is being politically correct,” he responded. “I don't frankly have time for total political correctness.”
"Frankly, what I say -- and oftentimes it's fun, kidding, we have a good time -- what I say is what I say," the Donald continued. "And honestly, Megyn, if you don't like it, I'm sorry."
Rosie O'Donnell herself had this to say: