Democratic presidential candidate Bernie Sanders speaks during a recent campaign event at Wartburg College in Waverly, Iowa. (Scott Morgan/Reuters)

CHARLESTON, S.C. — Democratic White House hopeful Bernie Sanders said Sunday that he is “very healthy” and will soon release his medical records, responding to a report that a prominent Hillary Clinton ally was preparing to press the 74-year-old senator to prove he's fit to be president.

“Of course we’re going to release our medical records,” Sanders said during an appearance on CNN’s “State of the Union.” “Thank God, I am very healthy. We will get medical records out the same way that Secretary Clinton has gotten her records out. It is not a problem.”

The issue came to the fore Saturday, after Politico reported that David Brock, founder of Correct the Record — a super PAC that defends Clinton — was planning to call on Sanders to release medical records ahead of the Feb. 1 Iowa caucuses.

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Clinton, who released her records in July, and Sanders are in South Carolina for a weekend of political events, including a crucial debate on Sunday night.

In response to the Politico report, Sanders sent out a fundraising appeal late Saturday in which his campaign manager, Jeff Weaver, called Brock’s reported plans “one of the most desperate and vile attacks imaginable.”

“They are insinuating Bernie is too old and unhealthy to be our next president,” Weaver said. “Let me be very clear with you: Bernie is in excellent health. But this personal attack is another example of sickness in our democracy when it is so easy for millionaires and billionaires to buy up candidates and elections.”

The Clinton camp sought to distance itself from Brock, with campaign chairman John Podesta posting on Twitter: “@DavidBrockDC chill out. We’re fighting on who would make a better President, not on who has a better Physical Fitness Test.”

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Clinton, who also appeared on CNN’s “State of the Union” on Sunday, laughed when host Jake Tapper asked her about the episode.

“I don’t know anything about it,” she said, “but I’ve released my medical records, and I remember being asked frequently for me to do so, and so, obviously, that’s something I’ll leave up to the Sanders campaign.”

During his segment, Sanders took issue with Tapper’s characterization of Brock as a Clinton “ally.” Sanders said that as “head of their super PAC,” Brock is more than that.