Eleven of 48 Senate Democrats have now decided to co-sponsor Sen. Bernie Sanders’s single-payer health care bill — just two years after Sanders could find zero co-sponsors for his legislation.

The bulk of the Senate Democratic caucus has not yet come around to Sanders’s Medicare-for-all bill, which is scheduled for release on Wednesday.

The majority of those backing Sanders’s Medicare-for-all bill tend to hail from blue states or are rumored 2020 presidential candidates. Still, as Vox’s Dylan Matthews has written, the endorsements are illustrative of a stunning shift among Democrats to embrace single-payer legislation — which was once circumscribed to the party’s far-left fringe.

In late August, Sen. Kamala Harris (D-CA) became the first Senate Democrat to back Sanders’s bill. She was quickly followed by Sens. Elizabeth Warren (D-MA), Sheldon Whitehouse (D-RI), and Kirsten Gillibrand (D-NY), as well as Cory Booker (D-NJ) and Brian Schatz (D-HI).

Sen. Tammy Baldwin (D-WI), who is up for reelection in 2018, became the first senator from a state won by Donald Trump in the general election to back the bill on Tuesday. (Though Wisconsin is a traditionally blue state that frequently elects Democrats.)

But several Senate Democrats have also said that they will not co-sponsor the legislation, and Senate Minority Leader Chuck Schumer has not formally stated a position on the bill.

Resistance to single-payer materializes

Single-payer is still meeting resistance in some Democratic circles, though, with a handful of Senate Democrats expressing opposition and a handful of others publicly saying that they have not made up their minds.

Sen. Sherrod Brown (D-OH), widely seen as one of the most progressive senators in a red state, said that he would not be co-sponsoring the bill — though he is pushing a health care bill of his own aimed at expanding Medicare by lowering the enrollment age down to 55. Brown is expected to face a difficult reelection race in 2018.

“Right now, I’m focused on building bipartisan support for my bill to allow people to buy into the Medicare program at age 55, which will cut costs and expand choices for Ohioans,” Brown told Vox in an email.

Similarly, Sen. Tim Kaine (D-VA), Hillary Clinton’s vice presidential running mate in 2016, appeared to confirm in an interview that he wouldn’t be co-sponsoring the bill, citing his preference to give consumers options in choosing their health insurance. (Sanders’s single-payer bill would likely eliminate private insurance companies and replace them with a single, government-run insurer.) Kaine supports a government-run public option, and said he wants enrollees to be able to pick between the government plan and a private plan.

Meanwhile, some Senate Democrats haven’t made up their minds yet. Sen. Chris Van Hollen (D-MD) said he needed to scrutinize the text of the (still unreleased) Sanders bill, and Sen. Ron Wyden (D-OR) said much of the same.

“I’m going to have to see the bill,” Wyden told me in the Capitol Monday evening, adding that his focus right now was on evaluating if it was possible to implement single-payer at the state level.

Here’s Vox’s tally of which Democratic senators have announced their support for the bill: