WASHINGTON ― In the wake of the Republican failure to repeal the Affordable Care Act on Friday, leading figures in the progressive wing of the Democratic Party are rallying behind a single-payer health insurance and a raft of other bold reforms.

These lawmakers and grassroots leaders have long believed that the problems plaguing the Affordable Care Act, also known as Obamacare, are rooted in the original health care law’s attempt to accommodate, rather than gradually replace, the private, for-profit health insurance system.

Now that efforts to eliminate the law wholesale are effectively dead, they are again arguing that the best way to improve the country’s health care system is to confront the power of corporate health care providers more directly.

“We have got to have the guts to take on the insurance companies and the drug companies and move forward toward a ‘Medicare for all,’ single-payer program,” Sen. Bernie Sanders (I-Vt.) said on MSNBC’s “All In with Chris Hayes” on Friday night. “And I’ll be introducing legislation shortly to do that.”

Sanders added on CNN’s “State of the Union” on Sunday that he would “absolutely” seek President Donald Trump’s cooperation on expanding Medicare and lowering prescription drug prices.

Even before the Republicans withdrew their Obamacare repeal bill, Rep. Keith Ellison (D-Minn.), the deputy chair of the Democratic National Committee and a close Sanders ally, previewed this message at a rally in defense of Obamacare on Thursday.

“Don’t just be satisfied with defeating Trumpcare ― set your sights on creating real Medicare for all!” he told a cheering crowd of hundreds of activists. Ellison is a co-sponsor of a “Medicare for all” bill in the House.

Representatives of several major progressive organizations ― the Working Families Party, the Progressive Campaign Change Committee, Credo, Social Security Works and the National Nurses United ― all echoed this push in conversations with The Huffington Post on Friday and Saturday.

“The problem is the insurance companies, Big Pharma ― they’re gonna come back and use the chaos to their advantage,” predicted Social Security Works executive director Alex Lawson. “If Democrats go with a half-a-loaf policy, Republicans are going to blame them for the failures of Big Pharma. They have to immediately pivot to expanding Medicare.”

During the debate over repeal, Rep. Ro Khanna (D-Calif.) used some of his time during a Budget Committee hearing to note that if Trump wanted to follow through on his campaign promise to repeal Obamacare and replace it with something “terrific,” he could fall back on an idea Trump himself endorsed in a 2000 book: single-payer.

On Monday, Khanna said that now is the moment to drive the single-payer message home. “To resist Trump, we need to play offense and not just defense,” he told HuffPost.

“As I pointed out in the Budget Committee hearing on Trumpcare a few weeks ago, Donald Trump supported a single payer system modeled after Canada in 2000 in his book [The America We Deserve],” Khanna went on. “He knows that is the only system that would fulfill his promise of more benefits, more coverage, and less costs. We should have every Democrat quoting Trump on a single-payer system as a mantra, and support Senator Sanders and Congressman Welch in their vision for Medicare for All, or at least, a public option. Senator Sanders is the leader of the Democratic Party currently in offering a conviction-based, affirmative vision. We should follow his direction.”

Notwithstanding the support of the influential groups for the proposal and ― according to a May 2016 Gallup poll ― even a majority of the American people, Medicare-for-all legislation is a non-starter in the current Congress. Single-payer health insurance still lacks support from many, if not most, Democrats, let alone from the Republican lawmakers who control both chambers.

But the proactive strategy speaks to increasing confidence among progressives that if they stick to their ideals and build a grassroots movement around them, they will ultimately move the political spectrum in their direction.

“It does take time for social change,” said Chuck Idelson, communications director of National Nurses United, a 150,000-person labor union that has long advocated for a single-payer health insurance system.

NNU is partnering with Justice Democrats and Brand New Congress on an online petition campaign demanding that Democrats back Medicare for all. The union is also advocating for a state level single-payer plan that is making its way through the California legislature.

“We didn’t end slavery overnight,” Idelson said. “It took from Seneca Falls in 1848 ’til 1920 until women won the right to vote. But they only won it by building a movement.”

The Washington Post reported Sunday that activists around the country urged their representatives over the weekend to get behind a single-payer program.

Justin Sullivan/Getty Images Sen. Bernie Sanders (I-Vt.) is already planning for the aftermath of Republicans' legislative defeat with a push for single-payer health insurance.

In the meantime, a potential benefit of this ambitious approach is what’s known as shifting the “Overton Window” ― a political science term for the narrow range of acceptable political views at a given moment in time.

By adopting a position that is considered extreme by contemporary standards, politicians and activists can make more attainable policy goals start to seem reasonable by comparison.

That phenomenon already seems to be working in progressives’ favor.

Sen. Jeff Merkley (D-Ore.), the only one of Sanders’ Senate colleagues to endorse his presidential bid, discussed the possibility of lowering the Medicare eligibility age or empowering Medicare to negotiate drug prices in his statement on the Republican bill’s collapse.

“There are plenty of ideas already on the table that would make health care more affordable for working families, from a public option, to prescription drug negotiations, to offering older Americans the chance to buy into Medicare,” Merkley said on Friday. “I’m happy to work with anyone, from either side of the aisle, to explore these or any other ideas that would improve health care for working Americans.”

Lowering the Medicare eligibility age from its current level of 65 is a “very interesting” idea, because of the positive financial effect it would have on the Obamacare insurance exchanges, said Austin Frakt, a health economist for the Department of Veterans Affairs.

By allowing the oldest exchange participants to enroll in Medicare, lowering the Medicare age would relieve the health insurance marketplaces of some of their costliest customers, said Frakt, who also has academic posts at Boston University and Harvard.

“It would reduce the premiums in those markets,” he predicted. (Frakt noted, however, that absent measures to offset the cost of the additional beneficiaries, the change would increase Medicare’s financial burden.)

Social Security Works’ Lawson praised the idea as an incremental step toward Medicare for all.

“Start by lowering the age to 62 and get it down to zero,” he said.

Republicans, meanwhile, believe they can score points against Democrats on the issue.

“We aren’t even 3 months into the 2018 cycle and House Democrats have already begun calling for a single-payer healthcare system,” said Jesse Hunt, a spokesman for the National Republican Congressional Committee, in an email to reporters Monday.

“Obamacare is collapsing as a result of [its] top-down, government centered approach and the Democrats’ only answer is more government,” Hunt went on. “The question remains, how many other Democrats will join the chorus to appease the activist base of the Party that’s clamoring for far-left policies?”

If Democrats go with a half-a-loaf policy, Republicans are going to blame them for the failures of Big Pharma. Alex Lawson, Social Security Works

Another progressive policy gaining mainstream traction is legislation permitting the importation of prescription drugs from Canada, where the existing single-payer system keeps prices lower. Sen. Cory Booker (D-N.J.) was one of several Democratic senators to endure heavy criticism in January for helping block a resolution supporting drug importation. In late February, Booker became a co-sponsor of legislation Sanders introduced that would legalize prescription drug importation from Canada and other countries.

Trump talked about getting tough with pharmaceutical companies over the price of prescription drugs as recently as early January.

But he has remained silent on the matter since his inauguration, including the 17-day period when he was trying to pass House Republicans’ Obamacare repeal bill. What’s more, the ordeal cast serious doubt on Trump’s willingness to take on the GOP’s ultraconservatives, who no doubt would oppose any form of government intervention to reduce drug prices.

Trump now claims he is counting on Democrats to negotiate over Obamacare on his terms, since, in his telling, the law is on the brink of collapse.

Obamacare’s insurance exchange markets have major problems in some states and regions, but the nonpartisan Congressional Budget Office characterized them as stable overall.

Still, Senate Minority Leader Chuck Schumer (D-N.Y.) suggested in a CNN interview on Friday night that Democrats would be open to working with Trump and congressional Republicans on reforming the law.

“We’re not gloating that they failed. We’re sad that they won’t work with us to improve Obamacare,” he said.

Murshed Zaheed, political director of Credo, warned Democratic leaders that any Democratic efforts to work with Republicans would not get any help from grassroots groups like his.

“If Democrats want to push their version of so-called moderate proposals ― good luck to them,” Zaheed said. “I don’t think anybody should be under any illusion that Schumer or [House Minority Leader Nancy] Pelosi will get anything from collaborating with the right-wing extremists that control Congress.”

Ryan Grim contributed reporting. This story was updated Monday to include comments from Khanna and Hunt.