Republican presidential candidate Nikki Haley has said it is unlikely Joe Biden would “make it” to the end of a second term were he to be re-elected to the White House.
Mr Biden, 80, announced he was running for re-election in 2024 on Tuesday.
He is already the oldest president in history. By the end of a second term, Mr Biden would be 86.
“He announced that he’s running again in 2024, and I think that we can all be very clear and say with a matter of fact that if you vote for Joe Biden you really are counting on a President Harris, because the idea that he would make it until 86 years old is not something that I think is likely,” Ms Haley said in a Fox News interview on Thursday.
She was referring to President Biden’s deputy, vice president Kamala Harris, who would take over the presidency if Mr Biden died in office. The vice president featured prominently in a video which launched Mr Biden’s re-election bid.
The White House issued a blunt response to Ms Haley’s comments, NBC News reported.
Deputy press secretary Andrew Bates said: “As you know, we don’t directly respond to campaigns from here. But honestly, I forgot she was running.”
Some Democratic voters have indicated they would prefer he not run, in part because of his age – concerns Mr Biden himself has called “totally legitimate”.