One could argue that it has already proved problematic for Senator Elizabeth Warren, who has been one of Medicare for all’s top champions in this race, along with Senator Bernie Sanders, who has been touting the idea nationally since his 2016 presidential run. Under pressure to explain how she would pay for her proposal, in November Ms. Warren released a detailed accounting of where the estimated $20.5 trillion that her plan would cost over 10 years would come from.

Her financing plan drew heavy fire as misguided and unrealistic, including from some of her Democratic competitors. Former Vice President Joe Biden’s campaign dismissed it as “mathematical gymnastics,” while Mr. Sanders charged it wasn’t progressive enough and would “have a very negative impact on creating jobs.” Around this time, Ms. Warren’s poll numbers and fund-raising took a turn for the worse.

Even among Democrats, Medicare for all polls worse than the less revolutionary alternatives of the sort being offered by Mr. Buttigieg and others, including Mr. Biden and Senator Amy Klobuchar.

And yet, the fight goes on. Many observers have noted that the Democratic debates — especially the first ones, which felt like a rolling seminar on medical insurance policy — have devoted a disproportionate amount of time to the candidates slashing at each other over who has the political courage — or naïveté — to go big on health care.

This has produced some fiery clashes, as when, in the October debate, Ms. Klobuchar suggested that Ms. Warren didn’t know “the difference between a plan and a pipe dream.” But more broadly, it is miring the Democrats in an unnecessary fight over a policy proposal that is divisive and that would require a political miracle to achieve without a progressive takeover of the Senate. And even then, it would most likely be difficult — remember how hard it was to pass Obamacare even with Democrats controlling both chambers?

Yes, the Democratic candidates need to talk about health care. Polls show that it is a top — if not the top — policy concern for their voters, and the issue was a pillar of the party’s successful platform to win control of the House in 2018. But there are other health care matters that could use more attention, such as surprise medical bills, reproductive rights and the Republicans’ continuing efforts to dismantle Obamacare — which have gained far more traction than many people predicted, threatening coverage for millions of Americans.

With the Iowa caucuses less than a month away, Democrats need to move beyond the Medicare for all fixation. Enough time has been spent bickering over the particulars of an electorally risky proposal that is unlikely to come to pass, no matter who wins the White House.