Bernie Sanders
Former Democratic presidential candidate Senator Bernie Sanders (I-Vt.) speaks during a Capitol Hill rally to promote a people's agenda and a common commitment to stepping up grassroots mobilizations for economic and social justice and equality in Washington, D.C., Nov. 17, 2016. Reuters

Since last November's election, Democrats have been relegated to playing defense while Republicans, who control the House, Senate and White House, have been working to enact a conservative agenda. But after the GOP efforts to repeal and replace Obamacare fell apart Friday, Sen. Bernie Sanders, I-Vt., and the progressive wing of the Democratic party have used the Republicans' failure as an opportunity to push for a single-payer health care system.

"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," Sanders said on MSNBC Friday night. “And I’ll be introducing legislation shortly to do that."

Read: Bernie Sanders On 'Trumpcare': Defeat Of 'Trump-Ryan Health Care Bill' Touted As Major Victory

During a Saturday town hall in Hardwick, Vermont, Sanders promised to introduce legislation "within a couple of weeks," Vermont Public Radio reported. Rep. Peter Welch, D-Vt., said he would introduce similar legislation in the House, where Rep. John Conyers, D-MI, introduced a "Medicare for all" bill in January. Conyers' Expanded & Improved Medicare For All Act has more than 50 co-sponsors.

The progressive pivot toward a single-payer system highlighted a division among the progressive and moderate wings of the Democratic party, which was on full display in February when former Labor Secretary Tom Perez defeated progressive Congressman Keith Ellison, who co-sponsored Conyers' bill, in a vote to become the chairman of the Democratic National Committee.

While Sanders was calling for a single-payer system, Senate Majority Leader Chuck Schumer, D-N.Y., took a far more pragmatic approach. On Sunday, Schumer said he will work with Republicans to make improvements to existing law.

"We have ideas, they have ideas, to try to improve Obamacare. We never said it was perfect," Schumer told ABC's This Week. "We always said we'd work with them to improve it. We just said repeal was off the table."

Rep. Welch admitted any effort to move toward a single-payer health care system is almost certainly doomed to fail in the current GOP-dominated Congress. But universal health care has been a dream of the left since President Harry Truman first introduced the concept in 1945. Truman envisioned a national insurance system that would tax every working American and pay for medical costs, as well as wages lost while sick.

"Our doctors and hospitals would continue to deal with disease with the same professional freedom as now," Truman told Congress. "There would, however, be this all-important difference: whether or not patients get the services they need would not depend on how much they can afford to pay at the time."