By Ian Swanson and Jonathan Easley - 03/03/16 04:20 PM EST
The race for the Republican presidential nomination took another extraordinary turn Thursday, as 2012 nominee Mitt Romney declared 2016 front-runner Donald TrumpDonald TrumpTrump: I wish Ivanka and Chelsea Clinton weren't friends Poll: Clinton up by 6 nationally WATCH LIVE: Trump rallies supporters in Denver MORE unfit to serve in the White House.
Romney called Trump a fraud, ripped his policy proposals as nonsense and warned he would lead the country into a recession as president.
Hours later, Trump took to the stage with a litany of new insults for Romney, whom he has mocked as a loser because of his defeat to President Obama.
He noted his own endorsement of Romney in the 2012 cycle and used a crude joke to show how gladly it had been accepted at the time.
“He was begging for my endorsement. I could have said, 'Mitt, drop to your knees.' He would've dropped to his knees,’” the billionaire businessman said to a cheering crowd in Maine.
Romney’s robust speech was meant to be evisceration of Trump, and came just hours before a Thursday night debate where the front-runner will face off against the final three candidates who could prevent him from winning the nomination.
Trump is well ahead of his nearest rival, Sen. Ted CruzTed CruzVoting Trump because of the Supreme Court isn't enough Trump blames GOP as Dems top RNC ratings Dem lawmakers rally Muslims against Trump MORE (R-Texas), in the delegate count.
After the Super Tuesday contests this week, Trump has 319 delegates, according to The Associated Press, compared to 226 for Cruz.
Sen. Marco RubioMarco RubioFlorida: 'High likelihood' of first Zika transmission in the US Overnight Healthcare: Rubio presses Obama to spend Zika money | FDA moves ahead with trans fat ban The Trail 2016: Her big night MORE (R-Fla.), the GOP establishment’s presumed favorite, is well behind, with 110, while Ohio Gov. John Kasich has just 25.
Ben Carson, who is skipping the Thursday debate and has said he doesn't see a "political path forward," has eight.
The only way to prevent Trump from winning the 1,237 delegates needed to lock up the GOP nomination might be to defeat him in Ohio and Florida, which will hold winner-take-all contests on March 15.
Trump leads in polls of both states, though Kasich is close to him in Ohio. Rubio is promising a victory in Florida, where he is much further behind Trump in the polls.
Romney’s entry into the fight is part of a concerted effort by the celebrity tycoon's opponents to slow his momentum and prevent him from locking up the nomination in two weeks.
Super-PACs opposed to Trump have launched a massive advertising campaign against him in Florida.
Romney's attacks on Trump were strikingly personal.
“Donald Trump is a phony, a fraud,” the former Massachusetts governor declared. “His promises are as worthless as a degree from Trump University. He's playing the American public for suckers. He gets a free ride to the White House and all we get is a lousy hat.”
He argued Trump was born into privilege and squandered his inheritance through a series of frivolous investments.
“He inherited his business, he didn't create it,” said Romney, himself a wealthy entrepreneur. “And what ever happened to Trump Airlines? How about Trump University? And then there's Trump Magazine and Trump Vodka and Trump Steaks, and Trump Mortgage? A business genius he is not.”
He condemned Trump’s failure to completely disavow an endorsement from former Ku Klux Klan leader David Duke, arguing it would make the front-running candidate unelectable against Hillary ClintonHillary Rodham ClintonTrump: I wish Ivanka and Chelsea Clinton weren't friends Poll: Clinton up by 6 nationally Romney: Trump victory 'very possible' MORE if she wins the Democratic nomination.
Trump knew the attack was coming and responded in kind.
“Mitt Romney was a failed candidate; should have beaten Barack Obama easily,” he said on ABC’s Good Morning America.
Tweeting to his 6.6 million followers, Trump ticked through a point-by-point rebuttal, arguing that “Hillary wants no part” of him in a general election, and saying he’s uniting the party and bringing scores of new Republicans into the fold.
At a campaign rally in Portland, Trump called Romney a “disaster” as a candidate and a “choke artist.”
He said Romney “demeaned 47 percent of the country” with his infamous 2012 remarks about how 47 percent of the country votes for Democrats because they are looking for handouts.
The comments, secretly recorded at a fundraiser, are seen as a major reason for Romney’s defeat.
Trump said Romney thought about running for president again in 2016, but “chickened out because of me.”
It’s far from clear whether Romney’s onslaught against Trump will make a difference, but it highlighted the discomfort many Republicans have with the business mogul’s candidacy.
Observers have questioned whether the GOP is being broken apart by Trump’s rise, and if he wins, it’s hard to see the party unifying behind his candidacy.
Fox News founder Rupert Murdoch opined on Wednesday that the GOP would be “mad” not to unify around Trump if he wins the nomination.
Trump, for his part, has argued that he will bring the party together and bring in new voters.
At the same time, he’s signaled that GOP office holders should get in line.
On Tuesday, as he enjoyed his victories, he was asked about implicit criticism from Speaker Paul RyanPaul RyanApple's Tim Cook to hold fundraiser for Clinton Reid: Congress should return 'immediately' to fight Zika Classified briefings to begin for Clinton, Trump MORE (R-Wis.), who served as Romney’s vice presidential candidate.
Trump promised he could get along with Ryan, before adding that if he couldn’t, Ryan would “pay a price.”
Rebecca Savransky contributed to this story.