Sanders, the most popular figure on the American left, has used his higher post-election profile to advocate for single payer, while progressive firebrand Senator Elizabeth Warren has called single payer “the next step” for the party. Senator Kirsten Gillibrand has publicly said that “we should have Medicare for all.” Senator Kamala Harris, frequently buzzed about as a rising star in the party, recently told a crowd in her home state of California that “as a concept, I’m completely in support of single payer,” though she added the caveat: “but we’ve got to work out the details, and the details matter on that.”

Democrats are far from united over single payer, however. For the moment at least, Democratic congressional leaders are reluctant to endorse single-payer legislation. Senate Democratic Leader Chuck Schumer has been non-committal when pressed by reporters on single payer. House Democratic Leader Nancy Pelosi has not signed onto the House “Medicare-for-all” bill that has gained in popularity, though she has expressed support for the concept, and argued that states could act as laboratories for single payer. And talk of single-payer in the midst of the current congressional health-care fight has highlighted divides within the party.

“Single payer is a huge distraction from the enormously important task that Democrats have in front of them, which is defending Obamacare,” said Matt Bennett of the center-left think tank Third Way. “And assuming that Republicans don’t completely blow up the system, there’s a lot that needs to be done to shore it up. I think the fact that Pelosi and Schumer have stayed on the sidelines [over single-payer] is very telling. That might be a signal that leadership does not want to head in this direction.”

It’s not even clear how much Democrats who have embraced single payer would agree on if the policy debate moved from abstract discussion to nitty-gritty details. Locked out of power in Washington, Democrats have no ability to implement single payer. That gives liberal lawmakers the freedom to talk up the idea of government-administered, taxpayer-funded health insurance that would provide universal coverage, without necessarily needing to know exactly how they would achieve it.

“Democrats are essentially using ‘single payer’ as an easy shorthand to convey that they want a health-care system that works better and costs people less,” said Sherry Glied, a former health-policy adviser to the George H. W. Bush, Clinton and Obama administrations. “But just invoking the concept on its own doesn’t say much about policy specifics. To some extent, this is the flip-side of what Republicans did by advocating for repeal and replace [of the Affordable Care Act] when Obama was president. For Democrats, single payer may even be a more attractive proposition when there’s a Republican president since they don’t have to deal with the hard trade-offs that would be at stake if a bill could actually pass.”