Sen. Elizabeth Warren rolled out a $20.5 trillion health-care plan on Friday that sought to put an exclamation point on a central argument of her candidacy: that a liberal revolutionary can also be electable.

Warren’s plan, a version of the Medicare-for-all idea that has become a mantra for many on the Democratic Party’s left, includes a raft of new taxes on businesses and the wealthy but, she insisted, would not be funded on the backs of middle-class Americans.

The announcement followed weeks of Warren’s repeated refusal to say whether her plan would raise middle-class taxes, prompting criticism from rivals that the candidate known for her detailed proposals was afraid to concede the politically uncomfortable truth. The issue has been particularly awkward for Warren (Mass.), who has tried to overcome skepticism among some in the party who fear that her promise to radically restructure the American economy would alienate crucial swing-state voters.

On Friday, Warren appeared to try to thread the rhetorical needle. She vowed to spare most Americans from additional costs but positioned herself squarely on the side of embracing steep tax hikes — effectively daring President Trump, should she win the nomination, to brand her a tax-and-spend liberal.

“Health care is a human right, and we need a system that reflects our values. That system is Medicare-for-all,” Warren wrote in a Medium post published Friday. “A key step in winning the public debate over Medicare-for-all will be explaining what this plan costs — and how to pay for it.”

Centrist Democrats moved swiftly Friday to sound the alarm that Warren, who leads the pack in recent early-state polls and has amassed what many see as the most effective Democratic campaign operation, risks handing the Republicans a major advantage.

Not only would Warren have to defend new taxes as part of her health plan — on top of roughly $5 trillion in new taxes she has already advocated to cover a range of other proposals — but she would be attempting to convince Americans to support virtually erasing more than 150 million private health insurance plans.

“The average Democrat in Ohio is going to say: ‘Wait a minute, I mean, how do you do that? How do you do all of that? Free this and free that? How does that happen?’ ” said Rep. Tim Ryan (D-Ohio), a moderate who recently dropped out of the presidential race. “We just want to beat Trump. That’s the revolution. Beating Trump.”

While not specifically commenting on Warren’s plan, House Speaker Nancy Pelosi (D-Calif.) used a television interview Friday to point to the potential electoral dangers for Democrats of backing such a program in 2020.

“I’m not a big fan of Medicare-for-all,” Pelosi told Bloomberg TV, adding: “Hopefully, as we emerge into the election year, the mantra will be ‘more health care for all Americans,’ because there is a comfort level that some people have with their current private insurance.”

Others chided Warren for backing herself into a corner by supporting an idea proposed by her main liberal rival, Sen. Bernie Sanders, the democratic socialist from Vermont, and then failing to consider how to fund it. Sanders has said that middle-class taxes would go up, though overall costs would go down.

Several other Democratic candidates back a “public option,” under which a Medicare-type plan would be available to everyone but would not be universal.

“She accepted Bernie Sanders’s Medicare-for-all program and then had to reverse engineer how to pay for some of it. But it’s not terribly persuasive,” said Sen. Michael F. Bennet (D-Colo.), another candidate for president.

Former vice president Joe Biden charged that Warren’s cost estimates were off by trillions and there was no reasonable path to paying for such a sprawling health care overhaul.

“She’s making it up. There is no way,” Biden said in an interview with “PBS NewsHour.”

Sanders remained silent on Warren’s proposal Friday, and his campaign declined to comment on it. His reaction will be a key test for those on the left, signaling whether Warren has hewed closely enough to Sanders’s ideas to win support from his voters if his campaign falters.

Warren endured sustained attacks from her Democratic rivals during the last presidential debate, in large part because of her inability to explain how she’d pay for Medicare-for-all. It was shortly after that Oct. 15 faceoff that her staff ramped up efforts to come up with a funding blueprint.

“After the last debate she, she felt like, ‘Okay, I’m going to dig in,’ ” said Rep. Pramila Jayapal (D-Wash.). Jayapal is the lead sponsor of the House version of the Medicare-for-all plan, and she has been having conversations with Warren about it for months.

She praised Warren’s efforts. “It’s just really clear that this is not a question of: Can we do it viably?” Jayapal said. “It’s a question of: Do we have the political will to take on the entrenched interests?”

Republicans were quick to pounce, providing a preview of what a general election could look like should Warren be the nominee. The plan will “hurt millions by eliminating their jobs and private health insurance while simultaneously bankrupting the country and hurting the quality of care,” said Steve Guest, a spokesman for the Republican National Committee.

The Daily Caller, a conservative news outlet, posted a political cartoon depicting Warren’s plan as a massive Trojan horse, one that looks appealing but contains “crippling taxation.”

Warren cited several experts in rolling out her plan, but others questioned its assumptions. Kenneth E. Thorpe, chairman of the health policy department at Emory University and an expert on Medicare-for-all, said Warren was significantly underestimating the costs.

He said the cost in new federal spending would be $35 trillion over 10 years, about $15 trillion more than Warren’s estimate. “There’s no way it’s $20 trillion. I don’t know why they’d put out that number,” Thorpe said. “The bottom line is, even with all the big numbers she’s got in there, you’re only getting 55, 60 percent of the way there.”

Warren did secure praise from key players on the left, a population she’s actively courting. Ady Barkan, an influential health-care activist who met privately with Warren in California over the summer, lauded her plan as “perhaps the greatest feat of public policy jujitsu that I have ever seen.”

Jared Bernstein, an economic adviser to Biden during the Obama administration, also praised the plan’s deftness.

“Politically, health-care reform can be the Afghanistan of domestic policy. You can get completely bogged down there,” he said, but Warren’s detailed plan provides a way out of the trap.

“When you don’t have an answer, you’re just going to kind of flounder around, and at this point she can she can very much argue, ‘Go read page 14 and appendix two, and then we’ll talk,’ ” he said.

The debate over health care is particularly resonant for Democrats because they say Republicans are vulnerable on the issue, due to their attempts to eliminate the Affordable Care Act, or Obamacare, which has grown increasingly popular.

Warren’s funding proposal mostly involves hitting corporations and the wealthy, including a provision that would require companies to send most of the funds they currently spend on employee health contributions to the federal government.

The plan also expands Warren’s signature wealth tax proposal, so that people with a net worth above $1 billion would pay a 6 percent tax rather than the original 3 percent. (Those with a worth of less than $1 billion but more than $50 million would still pay 2 percent.)

The plan would also cut military spending, and it would take advantage of what Warren says would be significant savings from eliminating the labyrinthine bureaucracy of private insurance.

Warren contended her plan does not include a tax on the middle class, a position some disputed. Rather, she said, it will result in a $11 trillion tax cut for working Americans. “Congratulations on the raise!” Warren wrote in her Medium post.

The senator also said that in coming weeks she will roll out a transition plan, adding, “Of course, moving to this kind of system will not be easy and will not happen overnight.”

Matt Viser contributed to this report.