Sen. Elizabeth Warren (D-Mass.) speaks in Washington in September 2017. At left is Sen. Bernie Sanders (I-Vt.). (Andrew Harnik/AP)
Opinion writer

Four months ago, I predicted that, with the exception of Sen. Bernie Sanders, the Democratic presidential candidates were likely to coalesce around the kind of health-care plan I described as “Medicare For Anyone (who wants it)."

This is distinct from Sanders’ version of Medicare-for-all: While a government plan would be open to anyone, it wouldn’t be mandatory for anyone. Though many candidates said they supported Medicare-for-all and had co-sponsored Sanders’s bill, they had also co-sponsored alternative ideas and were being vague enough that they had room to shift toward Medicare-for-anyone.

It hasn’t exactly worked out that way. Instead of a broad consensus on Medicare-for-anyone with Sanders (I-Vt.) on the outside, the Democratic candidates seem to be dividing into two sizable teams, with Sanders being joined by Sens. Kamala D. Harris (Calif.) and Elizabeth Warren (Mass.) in the Medicare-for-all camp (though those two haven’t yet released specific plans).

This intra-party debate is now entering a critical phase, as the policy and political implications of the various positions are being explored in detail. And some of the details are enough to make you wonder whether candidates such as Harris and Warren may try to find a way to back away from the kind of single-payer proposal Sanders is offering.

To be clear, I’m not saying they absolutely will. Both Harris and Warren have said that health insurers are essentially vampires sucking money out of the system while providing no extra value except as a middleman. As Warren has put it:

“Look at the business model of an insurance company. It’s to bring in as many dollars as they can in premiums and to pay out as few dollars as possible for your health care. That leaves families with rising premiums, rising copays and fighting with insurance companies to try to get the health care that their doctors say that they and their children need. Medicare for All solves that problem.”

When you’re on record saying that, it won’t be easy to embrace an idea that maintains private insurance, unless (like Sen. Kirsten Gillibrand), you argue that a public option is just a step on the path toward a single-payer system, which it will inevitably become as people abandon private coverage for a superior government plan.

Under Sanders’s plan, insurers would be barred from offering coverage that duplicates what the government plan covers. But since the government plan would cover almost everything, there would be almost no purpose to private insurance.

And here’s where things get complicated. A new NPR/PBS/Marist poll shows 41 percent support for Medicare-for-all, defined as “a national health insurance program for all Americans that replaces private health insurance.”

But a whopping 70 percent support for “Medicare for all that want it," defined as allowing “all Americans to choose between a national health insurance program or their own private health insurance.” Even 46 percent of Republicans said they support such a program.

I guarantee you every presidential candidate has seen that poll.

Supporters of Medicare-for-all would respond that it’s because people don’t fully understand the benefits of a single-payer system, and they might be right. But it’s also true that people fear change, and they fear losing what they have even for the prospect of something better.

It may also be, however, that all the discussion of Medicare-for-all has made Medicare-for-anyone — which just a few years ago would have been considered a radical idea — look like a centrist compromise. Liberals ought to at least consider that it could achieve most of their goals while being more politically palatable to many people than Medicare-for-all.

Consider, for instance, the plan from the Center for American Progress, known as “Medicare Extra for All.” It automatically enrolls everyone who’s uninsured and all newly born children in a new beefed-up version of Medicare (including dental and vision coverage, among other things), and allows employers and individuals to join if they want.

The Center for American Progress contracted with the consulting firm Avalere Health to assess the plan, and they concluded that by 2031 you’d have universal coverage with almost 200 million people on the new government plan, and you could do it without raising taxes on the middle class while bringing down overall health expenditures.

Which is both pretty darn good from a policy perspective and incredibly appealing from the perspective of a presidential candidate. While Republicans will of course call it “socialist,” just as they would any reform no matter how modest, it may not set off the same klaxons of fear among the electorate.

I could be wrong. Perhaps Sanders, Harris and Warren will offer a case for single payer that is compelling enough that they’ll win over a skeptical public. But it won’t be easy.

Read more:

John Delaney: Medicare-for-all is political suicide for Democrats

Heidi Heitkamp: Democrats, don’t ditch the ACA for Medicare-for-all

The Post’s View: No matter what Sanders says, there’s no Medicare-for-all without tradeoffs

Jennifer Rubin: Democrats should heed this warning on health care