Jill Biden said she had been “frightened” as she watched Joe Biden’s faltering performance during his 2024 presidential debate, and thought her husband might have suffered a stroke.

“I was frightened, because I had never, ever seen Joe like that before or since. Never,” the former first lady said in an interview with CBS set to air on Sunday.

“As I watched it, I thought: ‘Oh, my God, he’s having a stroke,’” she said. “And it scared me to death.”

Biden’s poor debate performance against Donald Trump in June 2024 sparked widespread alarm among Democrats, prompting calls for his withdrawal from the race.

Under immense pressure, Biden ended his re-election bid and endorsed his vice-president, Kamala Harris, leaving her just 107 days to campaign before the November 2024 general election against Trump.

Throughout the 90-minute showdown in Atlanta, a raspy Biden, then 81 years old, repeatedly stumbled over his words, took long pauses and mumbled inaudibly and occasionally incoherently.

At one point, his rambling response prompted Trump to quip: “I really don’t know what he said at the end of that sentence. I don’t think he knows what he said either.”

Biden memorably tried to land a blow on Trump’s policies on tax cuts and the national debt, but tangled the line and instead declared: “We finally beat Medicare.” His team later clarified that he had meant to say his administration had “beat big pharma”, but the misspeak crystalized longstanding concerns about the mental acuity and physical condition of the US’s oldest president.

Biden also veered away from a question on reproductive rights, shifting instead to references about women killed by immigrants – a pivot into one of his weaker areas and a point frequently emphasized in Republican talking points.

Jill Biden has remained a stalwart supporter of her husband throughout his decades-long political career. In a rally shortly after the June 2024 debate, Jill Biden praised her husband’s performance, saying: “Joe, you did such a great job. You answered every question. You knew all the facts.”

The former first lady will soon publish a memoir, titled View from the East Wing, about her experience in the White House. In it, she is expected to share her account of her husband’s fraught re-election campaign and his monumental – and historic –decision to withdraw.