Though 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 was diagnosed with pneumonia on Friday, the real concern is chronic dehydration, sources close to the Democratic nominee told Politico.

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“She won’t drink water, and you try telling Hillary Clinton to drink water,” a source said.

Clinton abruptly left a 9/11 memorial service in New York on Sunday because she felt “overheated.”

Video of Clinton leaving the event showed the former secretary of State struggling to walk to her van. At one point she appeared to collapse.

Sources told Politico that Clinton quickly recovered in the backseat of the air-conditioned van as she drank water and Gatorade.

Clinton, whose health has been under scrutiny, quickly called campaign staff and family to tell them what happened and assess the political fallout.