Sen. Jeanne Shaheen (D-N.H.) during a news conference in front of the Supreme Court in Washington on April 2. (Mandel Ngan/AFP/Getty Images)
Opinion writer

Axios reports:

[Sen. Bernie] Sanders will introduce a new version of “Medicare for All” today that’s even more ambitious than his last one — which was already more ambitious than any other health care system on Earth. . . . It would be the most robust system in the world, and one of the most centralized — a sea change from today’s largely privatized patchwork.

What it would mean for you: Sanders’ plan would move almost everyone — whether you’re on Medicare or Medicaid, or buy insurance on your own through the Affordable Care Act, or get it through your job — into a single government-run program.

You could not keep your existing plan.

What’s more, because the plan is so generous, covering “vision and dental, all with no premiums and no out-of-pocket costs (like copays and deductibles),” it would be enormously expensive. Of course Sanders doesn’t say how much tax revenue he would need or whose taxes would go up.

One would expect nothing less from Sanders, whose infatuation with centralized socialism would give President Trump the surest path to reelection. Likewise, no one is surprised to see progressive policy-wonk Sen. Elizabeth Warren (D-Mass.) add this to her collection of policy proposals. But for other candidates — Sens. Kamala D. Harris (D-Calif.), Cory Booker (D-N.J.) and Kirsten Gillibrand (D-N.Y.) — to co-sponsor the bill is, well, just plain foolish for a bunch of reasons.

First, they only enhance Sanders’s stature by announcing that they’ll follow him over the left-wing cliff. If voters really want this sort of undiluted government health care, why not vote for the “real thing” rather than an imitator?

Second, a nominee who embraces Sanders’s Medicare-for-all extremism jettisons the Democrats’ best issue (Trump will take away your health care) and gives him a big, fat target (socialized medicine). They go from offense to defense, from making the election about Trump to an election about how extreme the left really is. I would be hard-pressed to think of anything more damaging to Democrats’ chances in 2020.

Third, this also hands the tax issue back to Republicans. Sanders’s enormously expensive plan would demand an unspecified tax hike, most likely extending down to people who surely don’t consider themselves “rich.” Republicans, instead of defending their tax cuts for the rich, get to run on “Democrats will raise your taxes.” This might be a close second for the distinction of the move most damaging to Democrats’ chances of retaking the White House.

Fourth, it’s not necessary. Polling routinely shows that price, not universal coverage, is the defining issue for most voters. Moreover, though Medicare-for-all sounds good in theory, voters quickly sour on the idea when it becomes clear that they could lose the employer-provided coverage they like. By far, the most popular plans are those that expand on Obamacare.

Matt Bennett of the moderate Third Way group cautions, “Medicare-for-all may poll well in bumper sticker form, and it certainly gets a lot of likes on Twitter. But as we discovered in the ACA fight, health-care politics go much deeper, and when people learn the details of Medicare-for-all — like the $3.2 trillion per year price tag — support collapses.” He points out that, “of 967 television ads that Democrats in competitive House races ran in the 2018 general election, only two mentioned support for Medicare-for-all. Both of those candidates lost.”

Fifth, it’s never happening anyway. Unless Democrats win the House and Senate and get rid of the filibuster, this will never pass. Moreover, it’s far from clear that a majority of Democrats would support this, certainly not the scores of moderates who beat incumbents in suburban districts. Rather than unify Democrats, Sanders’s plan divides the party and puts the House majority at risk.

As I said, Sanders and Warren understandably want to go down this road. Their embrace of this kind of plan underscores their electability problems. However, for other candidates with the option to run from the center-left, this move suggests a lack of political realism and a gross misunderstanding of the electorate.

Bennett observes, “Democratic presidential candidates should be very, very careful about this. Their job is to win the nomination, rebuild the Blue Wall and beat Trump — it is not to ‘shape the debate.’ . . . There are plenty of robust health-care ideas out there that get us to universal coverage and control costs without socializing one-fifth of the American economy.” He adds, “Republicans are salivating to take on Democrats over M4A. They know Trump handed Democrats a gift on ACA repeal; their only hope is be rescued by Democrats own version of repeal and replace.”

Vice President Joe Biden surely won’t follow Sanders’s lead. Neither should Beto O’Rourke, Pete Buttigieg or other contenders who want to preserve his or her chances of winning the White House. As for Democratic voters, even those who theoretically might like Sanders’s ideological purity, this is an acid test. If they really want to win the presidency, they’ll need to look at the list of candidates not going down this road to political oblivion.

Read more:

The Post’s View: You can’t have it all — even with Medicare-for-all

Megan McArdle: Harris and progressives are pitching Medicare-for-all. They could give us four-more-years.

Catherine Rampell: We can figure out universal coverage without Medicare-for-all

Jennifer Rubin: Alternatives to Medicare-for-all that are worth studying and debating

Paul Waldman: Democrats have figured out where they’re going on health care