Sen. Bernie Sanders’ “Medicare for All” plan, unveiled last week, is an ambitious and (to many) enticing idea: a single, government-run health plan with generous benefits for everyone — just like most industrialized countries have enjoyed for decades.

If only it were feasible in today’s United States.

His proposal, which would eliminate almost all private insurance, will run into a wall of skepticism from ordinary voters — and not just conservatives who hate expanding the federal government.

Granted, most Americans agree that the government should guarantee that everyone has adequate health insurance. And, according to Kaiser Family Foundation polls, a growing number support a government-run “single-payer” plan as the way to do that.

But when the details are introduced, public opinion turns contrary. According to the same Kaiser polls, most Americans want better insurance, but they don’t want taxes to go up to pay for it. Most of them also dislike increasing government control over the health care system.

And most people with employer-provided private insurance say they like it — suggesting that they’d hesitate to see it scrapped for a government plan they’ve never used before. That’s what doomed Bill Clinton’s health care bill in 1994; that’s why Barack Obama left existing insurance plans pretty much alone. It’s not irrational; it’s simple aversion to risk.

I haven’t even mentioned the most immediate obstacle: A Republican-led Congress isn’t going anywhere near Sanders’ idea. Instead, Republicans are still trying to repeal President Obama’s health care law, which relies on private insurance companies. Their most recent bill, sponsored by GOP Sens. Bill Cassidy of Louisiana and Lindsay Graham of South Carolina, was teetering just short of a majority at the end of the week.

That’s why the most important health insurance bill to watch over the next few years may not be Sanders’ Big Bang approach, but a less ambitious proposal from Democratic Sen. Chris Murphy of Connecticut. He calls it “Medicare Buy-In.”

Murphy’s plan wouldn’t put everyone into a single government-run health plan. But it would give everyone access to Medicare, the enormously popular government-run plan mainly for those 65 or older. “Everyone” includes users of employer-provided health plans, who could buy into Medicare instead of whatever private plans their companies offered.

What’s the hitch? People would have to pay a premium, just as Medicare users do now.

It’s only a part-way measure, but politically it’s far more palatable than Sanders’ plan. People already know Medicare, if only through their parents or grandparents. Offering it as an option wouldn’t be a leap into the dark of a new and untried system.

Murphy isn’t the only Democrat working on an alternative to the Sanders plan. Sen. Brian Schatz of Hawaii has proposed allowing consumers to buy into Medicaid, and Sen. Debbie Stabenow of Michigan has proposed a more modest bill opening Medicare to anyone 55 or older.

If any of the options for expanding health insurance advance, the Vermont senator will deserve credit for making single payer part of the mainstream debate — and for making ideas that once seemed radical, like simply allowing everyone to buy in to Medicare, look downright conservative.

Doyle McManus is a columnist for the Los Angeles Times.