On Wednesday, Vermont Sen. Bernie Sanders introduced the Medicare For All Act of 2017, his long-awaited single-payer health care proposal that (as of this writing) has earned 16 Democratic co-sponsors. That’s a 16-senator improvement on the last single-payer bill he introduced in the Senate. It’s not just fellow lefties, like Oregon Sen. Jeff Merkley and Massachusetts Sen. Elizabeth Warren, supporting the Sanders plan. The bill has also earned the co-sponsorship of more typically cautious Democrats like New York Sen. Kirsten Gillibrand and New Jersey Sen. Cory Booker, as well as one senator, Wisconsin’s Tammy Baldwin, who’s up for re-election in a state Donald Trump won. It has become difficult for any Democratic senator considering a 2020 presidential bid not to co-sponsor Sanders’ bill, a sign that support for single-payer will be the default position.