To the left, to the left.

In the wake of a devastating electoral defeat that left their party in its weakest position in decades, the biggest names in Democratic politics are set to take one large step to the left on Wednesday with a formal endorsement of a single-payer health care system. It will mark the largest support for such a plan in more than a generation.

The Medicare for All Act of 2017, a 75-page bill that would transform America’s healthcare system by having the federal government insure everyone, will be introduced at 2 p.m. Wednesday by its author, Independent Sen. Bernie Sanders of Vermont.

In the past, Sanders’ crusade for a single payer system has been a lonely one. No Senators cosponsored his last government healthcare bill, or the one before that, or the one before that. But on Wednesday there will be at least six and potentially several more.

These cosponsors include the most prominent Democrats in the country — who are also keeping their options open for the 2020 presidential race — such Sens. Elizabeth Warren of Massachusetts, Cory Booker of New Jersey, Kamala Harris of California, Kirsten Gillibrand of New York, Sheldon Whitehouse of Rhode Island, and Jeff Merkley of Oregon.

Eyes on 2020

“Health care should be a right, not a privilege, so I will be joining Senator Bernie Sanders as a cosponsor on his Medicare-for-All legislation,” Sen. Gillibrand said in a statement Tuesday morning. And many other Senators like Chris Murphy of Connecticut and Brian Schatz of Hawaii are crafting proposals that, while less ambitious, would also dramatically increase the role of the federal government in health care.

All told, the Democratic Party’s leaders are moving to the left on health care.

Conventional political wisdom states that parties should move closer to the center following an election loss, especially after the drubbing Democrats took in 2016 from state legislatures to the White House. But many Democrats believe that the past moves to the center have so muddled the message that only a move to the left will clearly distinguish the party in the minds of voters.

They point to polls like this Washington Post-ABC News poll in July showing only 37 percent of registered voters believe the Democrats had any message besides being against Trump. Of people who voted for Barack Obama and then Donald Trump, 42 percent believed congressional Democrats would favor policies benefitting the wealthy while only 21 percent believed the same of Donald Trump, according to a recent survey by the liberal group Priorities USA.

But it’s unclear if moving to the left will address this problem.

“We welcome the Democrats’ strategy of moving even further left”

Republicans are giving no sign that they fear a party running on single payer and have attacked any Democrats who have expressed even just openness to it. “We welcome the Democrats’ strategy of moving even further left and we are happy to explain why they continue to lose after Election Day 2018,” Katie Martin, the National Republican Senate Committee’s Communications Director, told VICE News.

“We look forward to having a debate with Republicans about health care,” Sanders spokesman Josh Miller-Lewis told VICE News in response the Martin. “We have a better idea, backed by 60 percent of the American people: guarantee health care to all Americans as a right, not a privilege.”

Some Democrats including House Minority Leader Nancy Pelosi, however, are urging caution in the rush to embrace single payer. “Right now I’m protecting the Affordable Care Act,” Pelosi told the Washington Post on Tuesday. “None of these things, whether it’s Bernie’s or others can really prevail unless we protect the Affordable Care Act.”

Biggest push since Truman

The embrace of Medicare-for-All is a striking shift for the Democratic Party which has been gradually moving to the right on healthcare for decades in order to find a solution that could pass and not be easily vilified by the right-wing moniker of “socialized medicine.”

President Harry Truman proposed a national health care system seven months into his presidency in November of 1945, telling Congress that that healthcare “should be recognized as a public responsibility.” He had support of multiple Democratic Senators but ultimately abandoned the effort due to opposition.

President Lyndon Johnson then successfully passed some piecemeal government healthcare programs that covered the elderly and disabled, Medicare and Medicaid. President Bill Clinton tried his own health care bill which was attacked as a government takeover and did not make it to a vote. And Barack Obama finally passed a bill that was modeled on the Massachusetts plan crafted by a Republican Governor, Mitt Romney. But even that bill, which passed with no Republican support, led to a political backlash that swept the Republicans into power in the House.

That bill, known as Obamacare, expanded Medicaid and heavily subsidized the private market for individuals which brought down the uninsured rate to 8.8 percent, according to data from the Census Bureau released Tuesday.

Sanders’ “Medicare for All” bill would cover the last 8.8 percent, which is 28.1 million people, but at a substantial cost that Republicans will argue will increase the national debt and create inefficiencies in the market.