“I was frightened, because I had never ever seen Joe like that before or since. Never,” she told “CBS News Sunday Morning” as part of an interview airing this weekend.

“I don’t know what happened,” she said in the clip released Wednesday. “As I watched it, I thought, ‘Oh, my God, he’s having a stroke.’ And it scared me to death.”

In the debate, then 81-year-old president Joe Biden stumbled on his words, stared open-mouthed and lost his train of thought as he struggled to counter his bombastic rival.

Yet immediately after the debate, Jill Biden praised her husband’s performance, telling him in front of a crowd of supporters: “Joe, you did such a great job. You answered every question, you knew all the facts.”

Joe Biden’s debate performance sparked intense concern within the Democratic Party over his evident decline, ultimately leading to his exit from the White House race in favour of then-vice president Kamala Harris.

She lost to Trump following an abbreviated campaign.