On Wednesday, Sen. Bernie Sanders will introduce a new version of his long-standing proposal to provide “Medicare for All,” creating single-payer health insurance system that ends the private insurance industry as we know it.

Unlike the last time Sanders introduced similar legislation, he will have a co-sponsor. And not just one. Several potential candidates for the 2020 Democratic presidential nomination—and therefore, potential rivals to Sanders—have signed on, including Sens. Cory Booker, Kristen Gillibrand, Kamala Harris, Jeff Merkley and. Elizabeth Warren. (Sen. Chris Murphy may as well, even though he’s shopping his own plan for letting people buy in to Medicare as a step toward Medicare for All.) Meanwhile, over in the House, single-payer legislation has, for the first time, a majority of the House Democratic Caucus on board.

The Democratic Party now is, for all intents and purposes, the party of single-payer health insurance.

Big mistake.