WASHINGTON — The seismic shift in support for Sen. Bernie Sanders’ plan to transform the U.S. health care system into a single-payer program indicates the reach the Vermont independent has within the Democratic Party.

At the same time that his onetime presidential foe Hillary Clinton is reminding people of the party’s devastating loss last fall, Sanders is trying to define its future. His bill to enroll every American in Medicare drew 16 co-sponsors, 16 more than when he first introduced similar legislation in 2013.

It has garnered support from possible 2020 Democratic presidential hopefuls — Sens. Cory Booker of New Jersey, Kamala Harris of California, Elizabeth Warren of Massachusetts and Kirsten Gillibrand of New York — as well as Sen. Tammy Baldwin of Wisconsin, an incumbent up for re-election next year in a state narrowly won by President Donald Trump.

It also provided a welcome talking point for Republicans who have long railed against government-run health care. Several GOP senators used Sanders’ legislation as a tool to warn voters of what could come if Republicans are unable to overhaul the health care system.

During a bill introduction Wednesday that felt more like a campaign rally than the standard press conference, Sanders — flanked by co-sponsors — stuck to his standard script of bashing Republicans and special interest groups for doing nothing to address rising health care costs.

“The crisis we are discussing is not really about health care,” he told a crowded room of activists and supporters. “The crisis we are discussing today is a political crisis which speaks to the incredible power of the insurance companies, the drug companies and all those who make billions of dollars off of the current system.”

There is a divide within the Democratic Party on how to define such a system, and many Senate Democrats have yet to voice their support for Sanders’ plan, including vulnerable incumbents up for re-election such as Sen. Joe Manchin III of West Virginia.

Despite those differences, however, the expanding coalition of Democrats who now back such a proposal is a display of just how Sanders, who gave Clinton a serious challenge for the presidential nomination, continues to influence the national party.

“Sen. Sanders’ presidential campaign was a phenomenon that very few people saw coming. It uncovered a groundswell of progressive activation that the party now rightly wants to tap into as we head into 2018 and 2020,” Connecticut Democratic Sen. Christopher S. Murphy said. “I think that Democrats now feel a little freer to imagine some even bigger and bolder ideas.”

Asked whether the growing support for his legislation is indicative of his influence, Sanders hedged.

“Right now, we are focusing on what the bill is about,” he said. “We’ll talk about the politics of it later.”

Several other Democratic senators supported the national party embracing more bold ideas — like Medicare for all — in the fallout from the 2016 election and tied that movement directly to the success of Sanders’ campaign.

“It’s an idea whose time has come. There’s a clear recognition that universal coverage has to be the goal,” Democratic Sen. Richard Blumenthal of Connecticut said. “These principles are now in the public mind, front and center, and that is due, in part, to the prominence that Bernie Sanders gave to them during the campaign.”

A Democratic aide echoed those thoughts and said the shift is indicative of a recognition that the party needs to be bolder and sharper in its proposals.

“I think there will be a lot of support for this bill,” the aide said. “It’ll make the clear contrast between the two parties on health care even more clear.”

While other Democratic lawmakers also said they hoped support for the Sanders bill would not be a political benchmark for the party, several openly said endorsing the concept would be crucial for any successful candidate.

“I have trouble seeing how a viable Democratic candidate does not support the idea of single-payer,” Blumenthal said. “This bill is going to drive the national message.”

Some Senate Republicans, who this summer failed in their attempt to repeal and replace the 2010 health care law, are making a last-ditch attempt to overhaul it.

Sens. Bill Cassidy of Louisiana, Lindsey Graham of South Carolina, Ron Johnson of Wisconsin and Dean Heller of Nevada are pushing legislation that would transform the health care system to essentially a large federal block grant to the states based on the size of their individual insurance pool.