Republican presidential candidate Donald Trump responded to Mitt Romney's searing broadside on Thursday with one of his favorite put downs in the race for the GOP nomination.

"He's a choke artist," Trump said at a rally in Portland, Maine, referring to the former GOP presidential nominee's failure to defeat President Barack Obama in 2012. "We cannot take another loss. Mitt is indeed a choke artist."

Romney lambasted Trump earlier in the day, calling the businessman a "phony" and a "fraud," and accused him of "playing the American public for suckers." The speech was a stunning development and the clearest sign yet that the GOP is fracturing over its new front-runner after his dominating performance on Super Tuesday.

In his speech on Thursday, Trump called Romney "a failed candidate" who "failed horribly" and claimed he "begged" for his endorsement during the 2012 presidential race.

"I could have said, 'Mitt drop to your knees.' He would have dropped to his knees," Trump said, to laughter from the audience.

Trump further mocked Romney for declining to run for the White House a third time due to the possibility of former Florida Gov. Jeb Bush (R) jumping into the race. Bush has since dropped out, due in no small part to Trump's taunts he was a "low-energy" candidate.

"Jeb Bush actually convinced Mitt not to run," Trump said. "Jeb! Jeb sold him. He's a good salesman. He's a high-energy salesman. Mitt was afraid of Jeb, because he was afraid he'd get the money."

"I will tell you the real reason Mitt chickened out -- it was me," he added, garnering applause from the crowd.

The real estate mogul then predicted that Romney will still make a play for the White House.

“Mitt is going to run,” Trump said. “There’s going to be a third attempt. I still think he has the desire to run, maybe at the convention."