At least 16 Democratic senators have embraced the health care system proposed on Wednesday by Senator Bernie Sanders of Vermont, which would expand Medicare to all Americans. The move signals that some Democrats are shifting left on health care.

Senators are arranged by their ideology scores. Those supporting the plan are highlighted. ← More liberal Less liberal → ← More liberal Less liberal → Notes: Ideology measurements are based on DW-NOMINATE scores , which are based on congressional votes. Senator Sanders is an independent, but has caucused with Democrats.

With Republicans in control of Congress, the bill has no chance of becoming law anytime soon. But it could serve as a political manifesto and a possible campaign platform for progressive candidates. In the House, about 60 percent of Democrats have endorsed a “Medicare for all” bill.

Six of the senators are up for re-election in 2018, and several are potential 2020 presidential candidates, including Cory Booker of New Jersey, Kamala Harris of California and Elizabeth Warren of Massachusetts.