Hillary Clinton Hillary Diane Rodham ClintonJoe Biden looks to expand election battleground into Trump country Biden leads Trump by 12 points among Catholic voters: poll The Hill's Campaign Report: Biden goes on offense MORE has had problems in the past with dehydration, her husband said Monday.

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Clinton's health has been the target of scrutiny after a video surfaced showing the Democratic presidential nominee leaving an event early Sunday and stumbling into a car.

Aides later said Clinton was "overheated." Her doctor said in a statement late Sunday that she is being treated for pneumonia and had become dehydrated.

"Rarely, on more than one occasion, over the last many, many years, the same sort of thing’s happened to her when she got severely dehydrated, and she’s worked like a demon, as you know, as Secretary of State, as a senator, and in the year since," former President Bill Clinton William (Bill) Jefferson ClintonGOP brushes back charges of hypocrisy in Supreme Court fight Battle lines drawn on precedent in Supreme Court fight Sunday shows - Ruth Bader Ginsburg's death dominates MORE said during a Monday interview with CBS' Charlie Rose.

"And she had two-and-a-half hard days before the day when she got dizzy. Today she made a decision, which I think was correct, to cancel her campaign day to take one more day to rest."

Aides said Clinton will be back on the campaign trail later this week.

The former president said there's no chance she will be absent for longer than that.

"I'll be lucky to hold her back another day," he said.

Clinton also rejected speculation that his wife could have a health issue more serious than dehydration.

"Well, if it is then it’s a mystery to me and all of her doctors," he said.