Plenty of people are singled out for blame in Hillary Clinton’s new memoir, What Happened, an election post-mortem that doubles as a cathartic score-settling exercise. James Comey, Barack Obama, Joe Biden, The New York Times, and a certain former K.G.B. officer all receive their share of criticism for Clinton’s traumatic loss. But no 2016 foe apparently occupies so much of Clinton’s headspace as Senator Bernie Sanders, the Democratic socialist from Vermont who, she argues, hijacked the Democratic primary and derailed her White House bid by misleading voters with his utopian, pie-in-the-sky proposals for free health care, free college, and free ponies for all. “Throughout the primaries, every time I wanted to hit back against Bernie’s attacks, I was told to restrain myself,” Clinton writes, comparing Sanders at one point to the deranged hitchhiker in There’s Something About Mary. “Noting that his plans didn’t add up, that they would inevitably mean raising taxes on middle-class families, or that they were little more than a pipe-dream—all this could be used to reinforce the argument that I wasn’t a true progressive.”

The frustration has continued to weigh on her, nearly a year after losing the presidency to Donald Trump. And in a string of media appearances over the past week, Clinton has doubled down on her criticism of Sanders. During an interview with Vox’s Ezra Klein on Tuesday, the former secretary of state said that while she supports opening up Medicare, Sanders’s plans for a single-payer system have been unrealistic and devoid of details. “As you might remember, during the campaign he introduced a single-payer bill every year he was in Congress—and when somebody finally read it, he couldn’t explain it and couldn’t really tell people how much it was going to cost,” she said, arguing that the tax increases would likely be an insurmountable obstacle and noting that a similar plan had failed in Vermont. She continued the criticism in an interview with Pod Save America, complaining that Sanders’s indefensible claims “filled up a lot of space” during the Democratic primary and that it was “challenging to have a straightforward argument” about health care. “Because he would say: ‘Oh, we’re going to do single-payer.’ And I’d say, ‘Well, how are you going to do it?’ And he wouldn’t know.”

But while Clinton traverses the country insisting that she was unfairly outflanked by unserious ideas, Sanders seems to be winning that same war of ideas in Congress. In the past week, more than a dozen Democratic senators have signed on as co-sponsors of a Sanders-backed single-payer health-care bill, to be unveiled on Wednesday. Among the list flirting with the “Medicare for all” proposal are a number of lawmakers whose names have surfaced as potential 2020 contenders, including Elizabeth Warren of Massachusetts, Cory Booker of New Jersey, Kamala Harris of California, Al Franken of Minnesota, and Kirsten Gillibrand of New York. It’s hardly Sanders’s promised “political revolution,” at least not yet, but the party’s goal posts are suddenly shifting dramatically in his direction.

Clinton, who famously described herself during the campaign as “a progressive that likes to get things done,” rightly pointed out Tuesday that there are few details included in the latest Sanders plan. For starters, it remains unclear what “single-payer” means and how it would be paid for. But while Clinton remains worried that pushing for a single-payer system will distract from more achievable, incremental steps like a public option or expanding Medicare, Democrats in Congress are choosing not to get hung up on policy. Several senators have signed on to multiple competing visions for universal health care, choosing to win the political argument before hammering out the policy details. “[Sanders’s] bill is aspirational, and I’m hopeful that it can serve as a starting point for where we need to go as a country,” Franken said in a statement.

The sheer number of lawmakers that have signaled they are open to discussing a single-payer system suggests that it will continue to be a key issue as the race for 2020 heats up. It’s certainly a vindicating moment for Sanders, who didn’t manage to attract any co-sponsors for a similar bill back in 2013. And while neither House Minority Leader Nancy Pelosi nor Senate Minority Leader Chuck Schumer have backed the bill, there are signs it could soon become a litmus test for Democratic candidates. On Tuesday, Tammy Baldwin of Wisconsin became the first Democratic senator up for re-election in a state Trump carried to sign on to the proposal. Even Joe Manchin of West Virginia, which went for Trump by more than 40 points in 2016, said he is open to the idea of a single-payer system, though he expressed skepticism.