On Wednesday, Bernie Sanders introduced his much-anticipated Medicare for All legislation. It already has 16 Democratic co-sponsors, including potential 2020 hopefuls like Cory Booker, Kirsten Gillibrand, Kamala Harris, and Elizabeth Warren. A third of the Democrats in the Senate now back single-payer, a remarkable swing from just a few years ago. Back then, as Sanders himself put it, “we had me, and that was it.”

But even before Sanders released his plan, liberals were warning that Democrats would be unwise to shackle themselves to a bill that could hurt them politically. Bill Scher, writing in Politico, said the problem is that Medicare for All is “easier to say than to do. When grandiose promises on the campaign trail aren’t kept once attaining power, a party’s base becomes demoralized and recriminations follow.” Margot Sanger-Katz, writing in The New York Times, argued that Medicare for All could become the Democratic Party’s version of the GOP’s “repeal and replace,” an unfulfillable promise that would come back to haunt them:

Like “repeal and replace,” “single-payer” is a broadly popular slogan that papers over intraparty disagreements and wrenching policy choices. Republicans fumbled multiple attempts to replace the Affordable Care Act this year. If the Democrats eventually wrested back power, they could find themselves similarly factionalized and stymied over the details.

And in New York magazine, Jonathan Chait, writing after the bill’s release, said it would hurt Democrats on the campaign trail, too: “At no point does [Sanders] grant that the most important source of opposition will come from actual American voters concerned about losing their current plan or paying higher taxes.”

What these criticisms share is an underlying belief that Democrats are racing leftward on health care for short-term political gain—namely, appeasing the demands of the progressive base—without taking into account the long-term repercussions and whether Medicare for All is even feasible. But Sanders’s proposal is not a cynical slogan like “repeal and replace,” nor is it an inflexible roadmap that will invariably lead to a political dead end. It is better understood as a historic breakthrough in the way that Democrats approach health care, opening the door for all kinds of fixes to a system that nearly everyone agrees is too expensive and too inefficient.

Sanders’s bill would collapse all the existing ways that people get insurance—employer-sponsored, government-run (Medicaid and Medicare), Obamacare exchanges—into a single government plan. Private insurance would largely become nonexistent. The bill would eliminate deductibles and copayments. It would also overturn the Hyde Amendment by including access to abortion insurance.