 -- Donald Trump unleashed a tirade against Mitt Romney at his campaign rally this afternoon in Portland, Maine, saying the former presidential candidate held back from running this time around because of him.

“So when Mitt started raising his head a few months ago, I was very strong," Trump said. "I said, Mitt Romney should not run. He's a choke artist.”

Last year, Romney told supporters he would not run because it was “best to give other leaders in the Party the opportunity.”

“But I'll tell you the real reason he chickened out, it wasn't Jeb,” Trump argued Thursday. “It was me. I know this from people close to him.”

Trump also suggested that Romney may still have a desire to run.

“I think he probably still has a desire maybe at the convention to get some kind after thing. Hillary Clinton will destroy him in the election,” Trump said.

“I heard Mitt Romney made a fairly long speech," he said. "I’ll just address it quickly because it’s irrelevant."

"Look, Mitt is a failed candidate," Trump said of Romney, who was the 2012 Republican nominee against President Obama. "He failed. He failed horribly. He failed badly."

"And that was a race that I backed Mitt Romney. I backed him," Trump said. "You can see how loyal he is. He was begging for my endorsement. I could have said, Mitt, drop to your knees. He would have dropped to his knees. He was begging. True. True. He was begging me."

At the Hinckley Institute of Politics at the University of Utah Thursday morning, Romney delivered a searing speech attacking Trump’s policies, temperament, and calling him “a phony, a fraud.”

Trump fired back, calling the content of the speech “nasty” and the length “ridiculous.”

“So you help somebody and then he turns. Now, I will say this. He probably had a right to turn. Because nobody could have been nastier than me in getting him not to run. By saying he is a choke artist,” Trump added.

Former presidential candidate and New Jersey Gov. Chris Christie also addressed Romney’s comments at a press conference in Trenton, New Jersey.

Christie said though he and Romney politically disagree, he stands by his decision to endorse Trump, because he is the “best remaining candidate on the stage.”