Early in her campaign last year for the Democratic presidential nomination, where she cast herself as an experienced pragmatist against fanciful socialist Bernie Sanders, Hillary Clinton dismissed the Vermont senator’s proposal for single-payer health care. “I want you to understand why I am fighting so hard for the Affordable Care Act,” she told a Des Moines audience just days before the Iowa caucuses. “I don’t want it repealed. I don’t want us to be thrown back into a terrible, terrible national debate.... People who have health emergencies can’t wait for us to have a theoretical debate about some better idea that will never, ever come to pass.”

At the time, Clinton’s comments reflected the consensus of the party establishment: Single-payer was an appealing policy, but a pipe dream politically. After all, President Barack Obama had abandoned his support for the idea when he embarked on health care reform in 2009, knowing that many members of his own party would oppose it.

But a lot has changed in the year and a half since Clinton dismissed single-payer—a.k.a. “Medicare for all,” in which the government would pay for everyone’s health insurance—as pie in the sky. Democrats lost the White House, putting them fully in the minority and rendering all progressive policies as equally pie in the sky, at least for a few years. President Donald Trump, who promised voters he would “take care of everybody” on health care, is doing no such thing: Republicans are attempting, haltingly, to deliver on their years-long promise to repeal Obamacare, while also sabotaging the law to give truth to their lies that it’s collapsing.

“Democratic politicians I never thought would utter the words have mentioned single-payer to me in a non-joking way of late,” Len Nichols, director of the Center for Health Policy Research and Ethics at George Mason University, recently told Vox. As The New York Times reported last month, Democratic “leaders say the party has plainly shifted well to the left on the issue.” That’s true not only among the party base, as polling shows growing support for single-payer, but in Congress as well. Michigan Congressman John Conyers’s Expanded & Improved Medicare For All Act now has 113 co-sponsors, out of a total 193 Democrats in the House. And Sanders plans to introduce single-payer legislation in the Senate, where it will have the high-profile support of Elizabeth Warren and Kirsten Gillibrand, both 2020 presidential prospects who recently have urged the Democratic Party to embrace Medicare for all.

It’s an exciting moment for longtime advocates of single-payer, but a perilous one, too. A recent Kaiser Health tracking poll found that “while there has been a modest increase in the public’s level of support for single-payer in recent years, a substantial share of the public remains opposed to such a plan, and opinions are quite malleable when presented with the types of arguments that would be likely to arise during a national debate.” Recognizing this, Republicans are wasting no time in attacking single-payer. “Facing a widespread voter backlash over the House and Senate repeal bills,” The Washington Post reported last week, “they’re trying to make universal coverage a political anchor for Democrats by asking whether they can seriously defend trillions of dollars in new taxes and spending.”