Support for single-payer health care is on its way to becoming the consensus position in the Democratic Party.

This is particularly true after the debacle of the Republican health-care effort. Not only has the debate demonstrated that Americans are perfectly fine with the idea of government-provided health coverage, it has convinced Democrats that there's no point in trimming their political sails in the hope of getting buy-in from Republicans for whatever they advocate, so they might as well go all the way. When 500 or so Democrats run for president in 2020, we'll probably see many if not most of them drop the equivocation and come right out and say they favor single payer.

But before we get there, Democrats need to take a breath and do some thinking. Do they understand exactly what it is they want to advocate for?

Consider what has been going on in California. A bill to establish a single-payer plan in the state passed the state Senate there, but it was recently pulled in the Assembly by Speaker Anthony Rendon. Democrats have a super-majority in the legislature, so why didn't they go ahead? As Rendon argued, the bill would have created massive budget problems given other California laws; for instance, the state is required to spend 40 percent of its budget on education, so it would have had to come up with hundreds of billions of new dollars even beyond what it would spend on health care. It also would have required waivers from the Trump administration to divert money currently being spent by federal programs like Medicaid, waivers which of course would not have been forthcoming (David Dayen explains all the convoluted problems the bill would have created).

Nevertheless, some on the left treated Rendon's decision like the most perfidious treason against progressive principles. RoseAnn DeMoro, head of National Nurses United and a prominent Bernie Sanders supporter, tweeted out a picture of the California flag with a knife labeled "Rendon" sticking out of the bear's back, and characterized anyone who objected to the bill as in the pocket of insurance companies. When liberal blogger Kevin Drum criticized the bill as unrealistic, NNU's communication director sent him an email saying "the name of your magazine [should] be changed from Mother Jones — who actually fought for working people — to Milton Friedman, which would better reflect your class sympathies."

The truth is that establishing single payer in a single state is a nearly impossible challenge when the country as a whole continues to exist within our largely private system. It's why Vermont tried to do it and then abandoned the effort, why Colorado voters rejected it at the polls last year, and why it isn't going to work in California. Nevertheless, more and more in the future, single payer is going to be treated as a litmus test by which "true" progressives can be distinguished from establishment sellouts.

In the abstract, that's not such a terrible thing — health care is a vitally important issue that affects all our lives in profound ways, and it's one of the major dividing lines between the two parties. There's no reason why Democratic voters shouldn't use health-care policy as a means to judge prospective candidates, for president or anything else.

But everyone who cares about it needs a very specific and clear answer to this question: When you say "single payer," what exactly do you mean?

I suspect that many people don't actually mean single payer when they say "single payer." Liberals like myself have long lamented the fact that alone among the world's advanced industrialized democracies, the United States doesn't have a system that provides universal health coverage. We look around with jealousy at other systems that manage to cover everyone and produce health results that are equal to or better than what we get, all at dramatically lower cost. But those systems vary widely in design, and none of them are truly single payer.

In a true single-payer system, there is only one insurer, the government. It pays for all health care, and is able to use its regulatory and market power to hold prices down and take advantage of bureaucratic efficiencies. The country that comes closest to single payer is Great Britain, with its National Health Service. You might recall that Britons are so proud of the NHS that the opening ceremony of the 2012 London Olympics included a tribute to it.

But even the British system has some private elements to it. And moving to a completely public system from our current mishmash of public and private insurance (and mostly private health providers) would require an extraordinarily costly, complex, and lengthy transition. But maybe that's fine with you — you can argue that in the long run, that maximizes the benefits.

Or perhaps you would prefer a hybrid system like the one they have in France, where there's a universal government insurance program that covers everyone's basic needs, and then most people buy private but highly regulated supplemental insurance on top of it (Canada has something similar, but with much more control at the provincial level). That happens to be my preference, particularly since we can foresee a path to it from where we are now, by expanding Medicaid (which already covers almost 75 million Americans) and changing what private insurers provide but not eliminating them entirely. I think you'd have a hard time arguing that a hybrid system would be some kind of betrayal of progressive principles.

Or you might prefer a system like Germany's, where tax money goes to fund non-profit insurers ("sickness funds") that people can choose from. The point is, those are just a few of the options. Each country that has addressed this problem has come up with a slightly different solution (if you want to compare them, this is a terrific source), but what they have in common is that they all achieve universal coverage at a cost much lower than what we pay.

If we're going to remake the American health-care system — and we should — we're going to have to decide which of those models would work the best for us. But they're not "single payer."

I'll admit that like many people, in the past I've used the term "single payer" too loosely. And there's a rhetorical problem: We don't have a name that would refer to all the different kinds of universal health systems we might consider moving toward. It's hard to communicate what you're for in a simple and understandable way without such a name; it's much easier to say "I'm for single payer." But you probably aren't — or at the very least, you're open to any number of styles of health system, so long as they cover everyone in a way that's equitable.

We're now finally approaching a point where something we call single payer can be considered politically feasible. So we'd better make sure we know what we're talking about.