Joe Biden has confused former British Prime Minister Theresa May with her long-dead counterpart Margaret Thatcher for the second time since May.

Biden, 76, is the Democratic front-runner to challenge President Trump in 2020. The former vice president repeated his mistake of three months ago while addressing the Asian and Latino Coalition in Des Moines, Iowa, on Thursday.

In his speech, Biden attacked Trump for comments the president made following a clash between white supremacists and protesters in Charlottesville, Virginia., in August 2017. Biden said that Trump referred to white supremacists as "very fine people."

"Words that stunned the nation, and I would argue – I know – shocked the world. International leaders spoke about it," Biden said, referring to Trump’s Charlottesville comments.

"You had people like Margaret Tha… excuse me," Biden said, catching himself. "You had people like the former chairman and the leader of the party in Germany. You had Angela Merkel stand up and say how terrible it was. International leaders looked at us like, 'what in God’s name is happening to the United States of America?'"

Biden made an almost identical mistake at a fundraiser in May. He confused Margaret Thatcher, who left the Prime Minister’s office in 1990 and died in 2013, with Theresa May, who exited office earlier this year after failing to rally Parliament behind a Brexit deal.

“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.”

On this occasion, Biden did not correct himself by citing May, instead veering away to talk about Merkel.

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.

The May mistake came amid worries about his age after he slurred his words during his campaign announcement speech. In the opening weeks of his campaign, aides shielded him from reporters and he has continued to hold a much lighter schedule than other Democratic candidates.