“Medicare for All puts all health care on the government’s books. But Medicare for All is about the same price as our current path — and cheaper over time,” Warren argued, saying her plan would cost about $52 trillion over 10 years, compared to the $59 trillion projected if the U.S. health system remained the same. “That means the debate isn’t really about whether the United States should pay more or less. It’s about who should pay.”

Former Vice President Joe Biden's campaign blasted Warren's plan as "unrealistic" and "mathematical gymnastics." Deputy Campaign Manager Kate Bedingfield said that the new payments from employers amounted to "new tax of nearly $9 trillion that will fall on American workers."

But Warren’s new proposal, first reported by Fox News , is the most complete attempt yet by a candidate to flesh out a broad concept first proposed by Bernie Sanders and later embraced by Warren and several Democratic presidential hopefuls. It also goes beyond suggesting how to pay for abolishing all private insurance and putting hundreds of millions of people on a government plan. Because Sanders’ bill lacked key details that determine how much the overall system will cost — such as how much physicians, hospitals, and drug companies would be paid — Warren is proposing these details herself.

The most sweeping and controversial piece of her additions to Sanders’ bill is a pledge to pay most physicians current Medicare rates — which are much lower than private insurance rates but higher than Medicaid — and to pay hospitals slightly above Medicare rates. She argues that doctors will save money overall because they’ll be able to dedicate the hours they currently spend billing a swath of interlocking private and public insurance plans to providing care.

But medical providers who are already mobilizing against Medicare for All are likely to take this as a declaration of war.

Warren’s proposal to use comprehensive immigration reform to help pay for health care reform —particularly, the taxes that millions of currently undocumented immigrants would theoretically pay if given a path to citizenship — is also sure to draw scrutiny. She uses the bill the Senate failed to pass in 2013 as a model, and estimates that it would generate $400 billion towards paying for Medicare for All, even when taking into account the cost of providing health care for those immigrants.

And, in a nod to the importance of organized labor to the Democratic Party and unions' mixed reactions to single-payer, Warren proposes that companies that have collective bargaining agreements with their workers will get to pay less toward Medicare for All than companies with a non-unionized workforce.

Warren has been on the defensive the past several weeks as Democratic rivals have accused her of obfuscating on health care, which many polls show is the most important issue to Democratic voters.

“Your signature, senator, is to have a plan for everything — except this,” South Bend Mayor Pete Buttigieg said to Warren at the last presidential debate. He has continued to push Warren on the issue since, telling reporters earlier this week that “my concern about the plan she’s putting forward is not just the multi-trillion-dollar hole but also the fact that most Americans would prefer not to be told that they have to abandon their private plan.”

Buttigieg has proposed a version of a public option plan which he has dubbed “Medicare for All who want it.”

Warren’s latest plan is designed to try and reverse that dynamic and put her opponents on the defensive on health care.

“We need plans, not slogans,” she writes in what is likely an implicit swipe at Buttigieg, who has also not provided details on how he would pay for his health care plan. “Serious candidates for president should speak plainly about these issues and set out their plans for cost control – especially those who are skeptical of Medicare for All.”

She writes that other candidates opposed to completely eliminating the private health insurance industry — as Buttigieg, former Vice President Joe Biden, and Sen. Kamala Harris have all expressed — should “explain why the ‘choice’ of private insurance plans is more important than being able to choose the doctor that's best for you without worrying about whether they are in-network or not.”

It’s unclear whether Warren’s latest plan will be enough to regain her footing on the issue. Some progressive members of Congress leading the charge for Medicare for All told POLITICO before the plan was released that they were skeptical that releasing a detailed financing plan made sense practically or politically.

“The tough part is that you need a CBO score to outline the exact cost — we just went through that on the prescription drug bill. Until then you’ll have people proposing different numbers,” said Rep. Mark Pocan, a co-sponsor of the House Medicare for All bill who also co-chairs the Congressional Progressive Caucus. “The bill hasn’t gone through the legislative process yet, so it’s disingenuous to say this is the only plan to pay for it. But if it provides comfort to some to see the options, fine."

Sanders himself has taken that details-lite approach to financing the health care overhaul. Instead of a set plan, he released a menu of options to pay for the system earlier this year, and recently said he doesn’t feel the need to do more.

“You’re asking me to come up with an exact detailed plan of how every American — how much you’re going to pay more in taxes, how much I’m going to pay. I don’t think I have to do that right now,” he told CNBC this week.

Warren writes that “ambiguity” in Sanders’ bill has “also allowed opponents of Medicare for All to make up their own price tags and try to scare middle class families about the prospect of tax increases.” Warren suggests that she is doing the work that Sanders' team has not. “I’m filling in the details and releasing a plan that describes how I would implement the long-term policy prescriptions of the Medicare for All Act and how to pay for it,” she writes.

Sanders has largely avoided the attacks and scrutiny that Warren has sustained, however, because he has bluntly acknowledged that taxes will likely go up on the middle class in order to help pay for the plan. He implicitly pushed Warren to join him at the last debate, saying, “At the end of the day, the overwhelming majority of people will save money on their health care bills. But I do think it is appropriate to acknowledge that taxes will go up.”

But Warren, perhaps with an eye on the general election, when pledging middle class tax hikes could be more of a liability, repeatedly refused to join Sanders.

“No middle class tax increases,” she writes in her post, before trying to reframe the $20.5 trillion government program as something of a tax cut, since hundreds of millions of people will no longer have to pay premiums, deductibles, or hospital bills. “$11 trillion in household expenses back in the pockets of American families. That’s substantially larger than the largest tax cut in American history.”