Sen. Elizabeth Warren’s once-ascendant presidential campaign has begun to dim. And among her fellow Democrats, including those in the field, there is a universally agreed upon culprit for the stall in the polls: her embrace and handling of Medicare for All.

The senator’s decision to back single-payer health care has long been considered by establishment Democrats as a self-inflicted wound, one that would prove to be a massive weight on her in a general election should she get there. One senior Democratic Party member—who is philosophically supportive of Warren’s candidacy—said he was “dumbfounded” by her decision to align herself so closely with the proposal. “She’s completely boxed herself in,” the member said. “I just don’t see why she did it or how she gets out of it.”

Both Warren supporters and Medicare for All advocates have dismissed such prognostications as the bed-wetting cynicism of a timid—and corporate-influenced—consultant class. And through it all they’ve had an easy rejoinder to the collective freakout: Beyond the moral argument for Medicare for All, polling has continually showed it to be popular.

But that now appears to be changing. A new national Quinnipiac University poll of the Democratic primary field showed Warren slipping dramatically, down 14 percentage points from their survey one month prior. And tucked into the survey was a possible explanation as to why. The pollsters tested support for Medicare for All and found that only 36 percent of the public said it was a good idea (52 percent said it was bad) compared to March 2019, when 43 percent said good idea, while 45 percent said bad.

Singular polls are bad barometers for the state of elections or politics in general. But other polling paints a similar picture. The Kaiser Family Foundation, which has been tracking public opinion on health care policy closer than anyone else, has recorded a majority support for a national health care plan—styled as Medicare for All—for years. But they noted that “the level of support has narrowed in recent months.” And the most recent data found that “more Democrats and Democratic-leaning independents would prefer voting for a candidate who wants to build on [Obamacare] in order to expand coverage and reduce costs rather than replace [Obamacare] with a national Medicare-for-all plan.”

Whether Warren’s regression and the fall of support for Medicare for All is a matter of correlation or causation has become the topic of intense internal debate in Democratic circles. And for the Senator’s more moderate competitors in the primary, the conclusions are fairly easy to draw: the shifting tides of opinion on health care are damaging her candidacy.

“I think it’s that Medicare for All is poison,” said a senior aide to another 2020 Democrat. “It is fucking poison. You touch it, you turn to dust.”

Warren’s campaign declined to comment for this piece. But her supporters point to a different explanation for the data: Democratic elites are fearful of Warren’s general election prospects and are going after Medicare for All as a proxy.

“People really like Warren and on the merits, and they probably would pick her as the nominee,” said Adam Jentleson, a Democratic operative who may be the Senator’s most pugnacious supporter online. “But the biggest fear about her is electability and you had a month where those fears were exacerbated from the New York Times poll [showing Warren faring poorly in swing states] to people turning Medicare for All into an electibility issue.”

To that end, Jentleson noted that House Speaker Nancy Pelosi and former President Barack Obama have both aired their skepticism with Medicare for All in recent weeks—giving Democratic voters a permission structure to drift away from Warren’s candidacy. But for Warren’s fellow ideological travelers, the fact that party elites have come out in opposition to Medicare for All isn’t the only problem she faces. The manner in which she’s handled the policy has played a role, too.

The Massachusetts Democrat has taken a less than direct path toward championing the idea. Though Warren endorsed Sen. Bernie Sanders’ Medicare for All proposal while the two served together in the Senate, she spent months on the campaign trail not fleshing out her health care platform. It was only during the June debate that she formally took the plunge. On health care policy, she said, “I’m with Bernie.”

Far from simplifying matters, that declaration only compounded the questions, even more so as Warren refused to answer whether a hike in middle class taxes would be needed in order to pay for a plan with estimated costs ranging from $13 trillion to $34 trillion. At first, she strenuously made the point that such a debate was inherently illogical. Money is money and if one’s premiums and copays go down by a larger share than their taxes go up then, fundamentally, Medicare for All will be a net financial positive. It made no sense, Warren implored, to only consider the proposal through the prism of a tax bill.

Eventually, the pressure mounted enough that she introduced an actual plan to pay for her proposal. It avoided any hikes in middle class income taxes, but did so by making some generous assumptions for other revenue drivers, such as comprehensive immigration reform coming to pass and a massive spike in IRS enforcement filling up the government coffers.

The reception was mixed. Warren got kudos for actually putting a plan to paper. But the moderates in the party deemed it pie-in-the-sky stuff and—more problematically—Sanders supporters didn’t rush to her defense. Instead, the Vermont Independent questioned her plan to continue placing the cost burden on employers (Warren’s plan largely maintains the health care contributions such employers make but shifts them to a government health care system). Privately, his surrogates dinged her for buying into the proposition that simply raising taxes was politically untenable.

Warren gave them more fodder weeks later when she introduced the procedural component of her health care plan: a proposal to first pass a so-called public option for health insurance coverage (in which people would have the choice to buy a government plan) before, years later, shifting towards Medicare for All (in which no such choice would be available).

That Warren’s disjointed journey on health care policy has hampered her candidacy more so than the policy itself, may be evident by the fact that Sanders has seen his standing tick up slightly as Warren has stumbled. His team credits that, in part, to the perception that his commitment to issues like Medicare for All is viewed as more genuine than anyone else’s.

But other campaigns see Sanders’ candidacy as sui generis in Democratic circles. And Warren’s stumbles are being treated now as affirmation that going big on health care policy was a gamble that simply didn’t pay off.

"The more voters learn about what Medicare for All really means for their families and their pocketbooks, the less support it has,” said T.J. Ducklo, a spokesman for former Vice President Joe Biden’s campaign. “Democrats won the House of Representatives in 2018 on the back of a relentless campaign to protect the Affordable Care Act, and we're not going to beat Donald Trump in 2020 with an unpopular and ineffective message on the issue voters care most about."