“He’s not going to win Michigan,” said Rep. Rashida Tlaib, a Detroit-born member of Congress’ so-called “Squad” who has endorsed Sanders. “Michigan wants someone who doesn't take corporate money and isn't bowing to corporations. Somebody who comes from corporate industry in that way, I'm not sure they're going to understand the impact of some of those policies they advocated for in the past.”

To Buttigieg’s supporters, the assault is more than a stretch: They’ve argued that he was just a junior staffer at the time and stopped consulting Blue Cross Blue Shield of Michigan in 2007, well before it cut jobs. Still, in a political climate where lawmakers and presidential candidates routinely invoke health insurers as evil vultures preying on sick Americans, the left found its opening.

“These attacks are false and irresponsible,” said Sean Savett, rapid response communications director for Buttigieg. “Pete’s work at Blue Cross Blue Shield consisted of three months of analyzing overhead expenditures — things like rent, utilities, and travel costs. His scope of work did not involve policies, premiums, or benefits. This was his first client study, so it largely involved on-the-job training to develop skills using spreadsheets and presentation software.”

Buttigieg has long argued that Sanders and Warren’s eat-the-rich message is “not unifying” and raised concerns about how policies such as free college would play in a general election. But by highlighting Buttigieg’s time advising the insurer to cast doubt on his ability to defeat Trump, progressives see a chance to take one of the young candidate’s main critiques of his left-wing rivals and train it back on him.

“If you helped a health insurance company lay off people in Michigan, Donald Trump is going to have a field day. Period,” said Adam Jentleson, a Democratic strategist with ties to the Warren campaign. “He likes to focus on questions of electability, and this is fatal in terms of electability.”

The attacks — which tend to frame his work in disqualifying terms — signal the degree to which progressives view Buttigieg as a threat to the most ambitious parts of their policy agenda. He’s poured more than $1.5 million into airing ads in Iowa criticizing Medicare for All and free college, and taken jabs at Warren for weeks. But even after the respected Des Moines Register poll showed him ahead in the first-in-the-nation caucus state in November, his rivals for the most part didn’t lay a finger on him.

That grace period in the primary is over: Buttigieg was forced to release his client list and make his fundraisers public this week after Warren criticized him for not being transparent. Sanders also criticized Buttigieg Tuesday in an Instagram video — an unusual step for Sanders — where he said Buttigieg’s shots at his free college proposal are “not accurate.” In addition, Sanders ribbed him for suggesting that the Vermont senator has “been too easy on upper-income people and the millionaires and billionaires” because Buttigieg has argued that the benefit shouldn’t be available to children of the wealthy.

Shortly after Buttigieg unveiled his client list on Tuesday, the progressive group New York Communities for Change organized a protest outside of one of his ritzy fundraisers in New York City. One activist’s sign read “Wall Street Pete.” The group, part of a coalition that has endorsed Sanders, is planning a second “emergency” protest at another Buttigieg fundraiser on Wednesday.

Murshed Zaheed, a former Harry Reid aide who is backing Warren, has taken to calling him “Pete Romney”: “Pete sort of invokes those soulless, white-collar, elitist D.C. politicians … They sort of paint themselves as whiz kids, but deep down they are essentially soulless, heartless technocrats for corporations who are just here to maximize profit.”

Staff on rival campaigns have also weighed in with clear attacks. “Some of the most prominent people who have been publicly attacking Medicare for All often seem to have direct ties to the health insurance industry that makes large profits off the current corporate system,” David Sirota, Sanders’ speechwriter, tweeted on Tuesday.

Like many Democratic 2020 hopefuls, Buttigieg had previously made positive remarks about Medicare for All before backing away from the plan. Last year, he tweeted: "I, Pete Buttigieg, politician, do henceforth and forthwith declare, most affirmatively and indubitably, unto the ages, that I do favor Medicare for All."

Earlier this year, however, he released his own competing plan he branded "Medicare for All who want it” — an optional public insurance model that would continue to charge patients premiums and fall short of full universal coverage.

At the same time, Buttigieg has ramped up his attacks on the single-payer model Sanders and Warren advocate, saying it would be too costly for taxpayers and strip Americans of their choice of insurance. In September, he began to cut ads going after the plan: “I trust the American people to make their health care decisions for themselves," one read.

Amid the backlash to the news of his work for Blue Cross Blue Shield before the company downsized, Buttigieg attempted to shift the spotlight to the jobs impact of Medicare for All — which would largely abolish the private insurance industry and ripple throughout the health care world, getting rid of the jobs of an estimated 1.8 million people. Warren and Sanders have proposed assistance to help those workers who are displaced by Medicare for All.

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Asked if his work led to layoffs on MSNBC’s Rachel Maddow Tuesday night, he said, “I doubt it. I don’t know what happened in the time after I left — that was in 2007 — when they decided to shrink in 2009.”

Then he added: “What I do know is that there are some voices in the Democratic primary right now who are calling for a policy that would eliminate the job of every single American working at every single insurance company in the country.”

But Medicare for All supporters who had become increasingly frustrated with Buttigieg’s rhetoric around single-payer say he shouldn’t be allowed to dodge questions about his past work for the health insurance industry and how it may inform his current positions.

"It certainly explains a lot," quipped Rep. Pramila Jayapal (D-Wash.), the lead author of the House Medicare for All bill who has argued vigorously against public option proposals like the one pushed by Buttigieg.

"I think he has a duty, if he wants to be a unifying Democratic presidential candidate, to really think about the criticism of his industry talking points against a movement that has over three-quarters of the Democratic Party on board and also a significant number of Independents in swing states. For him to parrot these industry talking points is a huge disservice and it's not, I think, the mark of a unifying president.”

And, in response to the campaign’s argument that Buttigieg was a lowly number-cruncher for McKinsey rather than a mastermind, critics point out that he touted the job as part of his political biography in the past, and argue the junior nature of the work is another reason he isn’t qualified to occupy the Oval Office.

“If that’s their argument — that 10 years ago he was a 25-year-old doing PowerPoints — then he has no business running for office,” said Zaheed.

