David Brock is expected to call on Bernie Sanders to release his medical records ahead of Sunday's Democratic debate. | AP Photo Clinton surrogate to demand Sanders release medical records But hours later, after this report provoked widespread criticism, her campaign distanced itself from David Brock’s planned tactics.

A top surrogate for Hillary Clinton is prepping a new attack in an intensifying and increasingly personal war against rival Bernie Sanders — calling on the 74-year-old to release his medical records before the Iowa caucuses on Feb. 1.

Clinton defender David Brock — founder of the Correct the Record PAC, which coordinates directly with Clinton’s campaign — is expected to hit the airwaves this weekend from Charleston, the scene of the third Democratic debate on Sunday night, and challenge Sanders to cough up a clean bill of health and doctor’s note in the next 16 days, according to a Democrat familiar with his thinking who was not authorized to preview any strategy.


Clinton released her medical records, showing she is “fit to serve as President,” last July. A spokeswoman for the Clinton campaign declined to comment on the strategy.

But hours later, after this report was published and Brock's planned tactics were widely criticized on Twitter, campaign chairman John Podesta distanced himself from the surrogate’s attack.

“@DavidBrockDC chill out,” Podesta tweeted Saturday night. “We’re fighting on who would make a better President, not on who has a better Physical Fitness Test.”

Podesta's belated comment also came after the Sanders campaign issued its own fundraising plea off of this report, calling it "a new, vile super PAC attack on Bernie."

The demand, sources said, reflects growing frustration within the Clinton campaign about a perceived lack of media vetting and public scrutiny of Sanders, just as polls in Iowa show a neck-and-neck race that has taken many in the Clinton campaign by surprise.

It marks a contrast from the first eight months of the campaign, when Clinton and her allies mostly ignored her Democratic rival and drew contrasts instead with the GOP candidates.

There is also internal frustration, a source said, about a dearth of surrogates willing to criticize Sanders on television. So far, the attack strategy has been carried out by the campaign itself, which has most recently scolded Sanders for failing to outline the details of his healthcare plan. And principals, such as Chelsea Clinton, have charged that Sanders would “dismantle Obamacare.”

The sense in Clinton quarters that Sanders is not receiving the same level of scrutiny as the former Secretary of State feels all too familiar, reminding campaign veterans of eight years ago, when Clinton and her supporters said Barack Obama had not been appropriately vetted and was getting a free pass from the press.

This new attack strategy, focused on Sanders’ fitness for office, dovetails with focus group findings from Republican pollster Frank Luntz, who has seen voters raise age as a potential problem for Sanders. Clinton, 68, has also faced questions from the right about her age.

Brock, a Democratic source said, is expected to combine the health hit with more questions about the Vermont Senator's failure to release details for how he’d pay for his universal healthcare plan — creating a two-front assault meant to drive home the point that voters need more information before Feb. 1.

In Charleston, South Carolina, on Saturday, Sanders' campaign spokesman Michael Briggs said: "We had planned all along to release information from his physician before the caucuses and primaries and we will."

Sanders also responded to the Clinton campaign earlier this week, saying he plans to outline details of his healthcare plan before the Iowa caucuses.

Sanders senior adviser Tad Devine said he was not surprised by a planned attack on Sanders' medical records. “These kinds of attacks are going to be employed by a super PAC that directly coordinates with her campaign,” Devine said, saying the campaign was trying to not get "distracted."

"Bernie Sanders has a message, that there’s a rigged economy, and that’s what we’re going to talk about," Devine said.

In an appearance on CNN Thursday, Brock cited polls that show one quarter of voters don’t know enough about Sanders to have formed an opinion of him, and called him a blank slate and said that his poll numbers would drop with more scrutiny. He drew a contrast with Clinton, whose emails, financial disclosures, and health records have all been made public over the course of her campaign.

So far, the attacks on Sanders from Clinton appear to be ineffective. His polling remains strong and the Washington Post reported last week that Sanders had collected $1.4 million in campaign contributions since Clinton began a series of attacks.