Sen. Bernie Sanders, I-Vt., may have lost his presidential primary challenge to Hillary Clinton last year. But he's winning the long game.

Case in point, Sanders plans to release a single-payer health care plan in September, and whereas he bore the brunt of a lot of bad press and intra-party fire during the 2016 campaign for his desire to see a national health care system, he's now gaining supporters left and right. On Wednesday, in fact, Sen. Kamala Harris – the California Democrat who has been on the receiving end of a lot of 2020 speculation already – endorsed Sanders' still unreleased plan.

"I'll break some news: I intend to co-sponsor the medicare-for-all bill because it's just the right thing to do," said Harris. "Somebody should tell my staff." She added later: "I think there's no question that we have to get to a point where all people have access to affordable health care … As we talk about moving towards a single-payer system, I think there is certainly momentum and energy around it."

Harris joins a cohort of other Democratic senators – most of whom have also been the subject of 2020 whispers – endorsing the move away from the kludgy, employer-based system on which American health care is currently built and toward single payer, including Sens. Elizabeth Warren, D-Mass., Kirsten Gillibrand, D-N.Y., and Cory Booker, D-N.J. Scores of Democratic House members, meanwhile, have signed onto a long-standing single-payer plan put forth by Rep. John Conyers, D-Mich.

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There is little doubt in my mind that any of this would be happening if Sanders had not had the success he did in 2016, which showed that a version of left-wing politics, long assumed to be dead and in its grave by the chattering class, may have a constituency after all.

Polling backs up the notion that Americans are at least single-payer curious. Kaiser's health tracking poll in July found that a majority favor it, an uptick that has "largely been driven by an increase among independents." An Economist/YouGov poll from the spring found majority support for expanding Medicare to everyone. A Morning Consult/Politico poll from around the same time found plurality support for having one government-based plan for everybody. Per the Pew Research Center, a full 60 percent of Americans "say the federal government is responsible for ensuring health care coverage for all Americans."

Now, I'm certain that one could poll this all differently and get different results, depending on phrasing and timing. But these results show at least an openness among the public for an entirely government-run system, contingent on the details, and a willingness to entertain an idea that plenty of pundits deride as totally foolhardy not because it's ill-advised, but because it's politically impossible.

There are plenty of factors at work here besides Sanders' efforts last year, of course. A legacy of Obamacare is that it cemented the notion that universal health care should and can be an achievable goal for Washington, even if the law as it currently stands doesn't get there. A least a part of the reason the Republican drive to repeal Obamacare fell apart is because of the political weaponization of data regarding just how many millions of people would find themselves uninsured under the various GOP plans. Each version Republicans put out was more politically toxic than the last, giving those members on the fence scant reason to fall in favor of it.

Meanwhile, America still spends the most money in the developed world for health care, without getting the best outcomes. And anyone who has ever interacted with an insurance company can surely chuckle at the idea that giving more of them more power is a good way to streamline the system. There's a reason government-run plans like Medicare or Medicaid are generally more popular than whatever hard-to-navigate and impossible-to-defend offering the nation's insurance giants are serving up.

Not that I think a single-payer plan is necessarily going to happen in the short term – or that implementing such a system doesn't have its own set of big challenges, or a cast of opponents who aren't all as unsympathetic as Big Pharma – but talking about it moves the national discussion in a positive direction, toward the aspirational and rational goal of having a system that works for everyone and that doesn't throw tons of money down into the maw of big insurance companies.

All that said, whether it's for ideological reasons or pure political expediency, Democrats today clearly feel the need to put single payer on the national stage. That's a win for expanding the limits of political possibility – it'll be up to the voters who care about these things to hold them to it when they're back in power, to push back on the tendency Democrats have to back big, progressive goals only when they can't happen.