Joe Biden flubbed the name of British Prime Minister Theresa May at a fundraiser Saturday night, calling her by former Prime Minister Margaret Thatcher's name.

Thatcher left office in 1990 and died in 2013. The mistake by Biden, 76, comes amid worries about his age after he slurred his words during his campaign announcement speech. Aides have shielded him from reporters. He leads early primary polls by a wide margin but the Democratic Party establishment has yet to swing behind him.

“Margaret Thatcher, um, excuse me, Margaret Thatcher — Freudian slip,” Biden said to laughter, according to a campaign pool report. “But I knew her too.” He then corrected himself by saying: “The Prime Minister of Great Britain Theresa May.”

Thatcher, who led the Conservative Party and was the first female British prime minister, served as prime minister during the 1988 U.S. election campaign. Biden made his first White House run then, but dropped out in late 1987 after backlash for plagiarizing a speech by Neil Kinnock, the U.K. Labour Party leader and a fierce critic of Thatcher.

Biden was speaking Saturday to about three dozen supporters at a $1,000-to-$2,800-per-person fundraiser in Columbia, S.C.

He used Thatcher’s name when telling the donors he had heard from 14 heads of state from around the world who’ve voiced concerns to him about President Trump. That list included Thatcher, he said, before correcting the “Freudian slip," saying he was referring to May. The U.K. head of state is Queen Elizabeth II, not the prime minister.

Biden was asked to assign a nickname to Trump and responded: “There are so many nicknames that I’m inclined to give this guy. We could just start with clown. When he says these ridiculous things he says, I mean this, I put my hand up and say, ‘Everybody knows who you are,’ because they do know.”

The former vice president said he wanted to run his campaign on a higher level. “The only place he [Trump] has any confidence is in the mud. The only thing he doesn’t know how to respond to is issues and specifics.”

At another point, Biden referred to Trump as a “no good SOB.”

Coincidentally, Thatcher became British prime minister exactly 40 years to the day before Biden was speaking. She entered Parliament in 1959 and was chosen as Conservative leader in 1975. She was first elected to Downing Street on May 4, 1979, and won reelection in 1983 and 1987 before being ousted by her own party after 11 years in office.

Biden’s citing of 14 foreign leaders who had supposedly expressed concerns about Trump is likely to be intensely scrutinized. Foreign leaders traditionally stay out of U.S. domestic politics.

He was vice president for two and a half months after Trump was elected in November 2016, and it is most likely that it was during this period — before Trump has been inaugurated — that he would have been speaking to foreign leaders. Any expressions of discomfort over Trump’s win would probably have been intended to have been private and prompt dismay that they have been used by him in an election campaign.

Biden told a South Carolina TV station it was fair to ask about his age. "All I say is watch me. Determine whether I have the energy or not to do it," he said. "But I have significant experience. I have learned a great deal. I have learned from the past.”