Washington (CNN) President Donald Trump's attorney Rudy Giuliani attempted to clarify his comments about Joe Biden in which he called the former Democratic vice president "a mentally deficient idiot."

"I didn't mean that. I meant he's dumb," Giuliani told CNN's Chris Cuomo during an interview Friday on "Cuomo Prime Time."

Asked about a potential Biden-Trump match-up in 2020, Giuliani told HuffPost in an interview posted Friday that "Joe Biden is a moron. I'm calling Joe Biden a mentally deficient idiot."

Meghan McCain, a co-host of ABC's "The View" and Republican Sen. John McCain's daughter, came to the former Vice President's defense on Friday.

"I am disgusted by Giuliani's abhorrent and idiotic comments about Joe Biden," Meghan McCain tweeted. "Joe Biden is one of the great political leaders of all time, one of the truly decent men left in politics - and someone my family has looked to for strength during the most difficult time in our lives."

I am disgusted by Giuliani's abhorrent and idiotic comments about Joe Biden. Joe Biden is one of the great political leaders of all time, one of the truly decent men left in politics - and someone my family has looked to for strength during the most difficult time in our lives.

A Biden spokesperson declined to comment in response.

"I was asked, 'Would (Biden) be a formidable candidate?' I said no," Giuliani told CNN on Friday. "He would be somebody that I think the President would like to run against. He never did well as a national candidate. The President did fabulously as a first-time national candidate."

Cuomo asked, "Do you really think Joe Biden is stupid?"

"No. In that category, I think he is," Giuliani replied.

Giuliani pointed to Biden's faux pas on the campaign trail and past plagiarism controversies, which he argued "indicates something even about character."

"I think the plagiarism is serious. I don't think he'll get beyond that," he said.

Biden's 1988 presidential race was upended after it was revealed he had lifted passages from British politician Neil Kinnock and other Democratic politicians, and he admitted as well that he had plagiarized while in law school.

On Saturday, Giuliani repeated the criticism while speaking to reporters after a campaign rally for Republican Rep. Dan Donovan, saying "everyone knows he isn't so smart, and it's a shame that people have such respect for him."

"Every decision he's made about foreign policy has turned out to be wrong, you know," Giuliani continued. "He didn't want to go into Iraq when they took over Kuwait, that was wrong. He did want to go into Iraq later and then he changed his mind then he wanted to divide Iraq into three parts. His, it's all coming about because he's a fun guy, but they only love him because he's a Democrat. If he were a Republican they would be going after him constantly."

Trump and Biden, a former chairman of the Senate Foreign Relations Committee, have been feuding this year in what seems like preview of a 2020 face-off.

Biden recently criticized Trump for an "inexcusable and irresponsible approach" in his summit with North Korean dictator Kim Jong Un and for giving the regime "many sought-after wins up front without getting anything in return."

Giuliani told CNN that Biden's statement was "vicious," but was not the reasoning behind his attack on the former vice president.

"Biden has a set of problems. So let's leave it this way -- I would prefer to see him as the candidate," Giuliani told Cuomo, adding that he would be worried if Democrats tapped a "surprise" nominee.