Former first lady Jill Biden said she was "frightened" by her husband Joe Biden's 2024 debate performance and thought he was having a stroke.

"I was frightened, because I had never ever seen Joe like that before or since. Never," Jill Biden told CBS News Sunday Morning's Rita Braver in an interview airing Sunday on CBS. 

"I don't know what happened," she said. "As I watched it, I thought, 'Oh, my God, he's having a stroke.' And it scared me to death."

Biden was running for a second term when he stumbled through the June 2024 presidential debate against Donald Trump, prompting widespread calls for him to drop out of the race. He dropped out a month later, with 107 days to go until the general election, endorsing Vice President Kamala Harris as the Democratic nominee. He became the first sitting president to pull out of a presidential race since President Lyndon B. Johnson stepped aside in March of 1968.

In a wide-ranging interview, Jill Biden talked about the election, her husband, her new book, "View from the East Wing: A Memoir," and more.

Watch more of Jill Biden's interview on "Sunday Morning" on May 31 at 9 a.m. on CBS stations and streaming on Paramount+.