The overriding priority for Democrats in selecting a candidate and platform for the 2020 election should be defeating President Donald Trump in his bid for a second term. Instead, a large segment of the party base is coalescing behind a candidate, Massachusetts Sen. Elizabeth Warren, whose central policy priority would drive voters to Trump.

More maddeningly, Warren and those backing her would risk Trump’s reelection for a policy proposal that has no chance of winning enactment.

We talk, of course, about Medicare for All. It is the child of Democratic Socialist Sen. Bernie Sanders of Vermont, but Warren has adopted it and has passed her progressive opponent in running with it toward the party nomination. That could well spell disaster for the Democrats.

If Medicare for All is a primary plank in the Democratic presidential platform, the Republicans’ usual charge of socialistic policies would no longer be hyperbole, but reality based. The 156 million Americans who have private health insurance would be asked to trust that the government can do better. Good luck selling that at the polls.

The $34 trillion in added costs for Medicare for All over the next decade would balloon the federal government’s share of the economy by 50%, meaning it would grow to around 27% of the economy, up sharply from the roughly 17% it has averaged in the Post-World War II era.

To her credit, Warren has tried to explain how she would pay for it all — new corporate taxes, a wealth tax on billionaires, military spending cuts — but it doesn’t add up. It would require higher taxes for all, including the middle class.

Many Americans are dissatisfied with the status of health care in this country. An estimated 27.5 million Americans have no medical insurance, 8.5% of the population. Addressing this unacceptable situation can be a campaign winner for the Democrats.

But history has shown that most Americans are averse to radical change when it comes to how health care is provided, paid for and regulated. Moderate voters in key swing states such as Michigan, Pennsylvania, Wisconsin and North Carolina could be scared into Trump’s camp by the prospects of a government takeover of insurance.

The fight might be worth it if such a policy change could happen. It can’t. Recall how hard the effort was to enact the Affordable Care Act — Obamacare — a relatively modest idea to expand Medicaid for lower income Americans and leverage the private sector system to provide better quality coverage to others. There is no way Warren, or anyone else, would have the votes to impose a national health care system.

The better course — the winning course — is to build upon Obamacare, through either offering a public option or giving older Americans, perhaps 50 and older, the option of buying into Medicare either individually or through their employer. Combined that with prescription price controls, another winner with voters.

In other words, gradual reforms with the goal of insuring all Americans.

Vice President Joe Biden, South Bend, Ind., Mayor Pete Buttigieg, and Minnesota Sen. Amy Klobuchar all line up, in various policy forms, with the public option approach. Of these candidates, Sen. Klobuchar could well prove the toughest Democrat for Trump to face but who, unfortunately, has not found much support among Democrats, at least according to the polls.

Democratic primary voters will need to recognize what is at stake. Progressive policies may increase the popular vote in solidly blue states. But the party cannot risk awaking Nov. 4, 2020 to find it has “won” an even larger popular vote victory than 2016, only to again lose the Electoral College by alienating voters in swing states. Frighteningly, that may be where things are headed one year out.

The Day editorial board meets with political, business and community leaders to formulate editorial viewpoints. It is composed of President and Publisher Timothy Dwyer, Executive Editor Izaskun E. Larraneta, Owen Poole, copy editor, and Lisa McGinley, retired deputy managing editor. The board operates independently from The Day newsroom.