Sen. Kamala Harris (D-CA) announced at a town hall on Wednesday night that she’ll be co-sponsoring Sen. Bernie Sanders’s (I-VT) upcoming single-payer health care bill.

Talking to 700 people at a church in Oakland, California, Harris became the first Senate Democrat to publicly announce her support for Sanders’s legislation, which is expected to be released in mid-September.

“I’ll break some news: I intend to co-sponsor the Medicare-for-All bill because it's just the right thing to do,” said Harris, who is widely seen as a leading Democratic presidential candidate for 2020. She added with a laugh: “Somebody should tell my staff.”

Sanders’s staff is still putting the finishing touches on the legislation, but it is largely expected to resemble the one from his 2016 presidential campaign. Hillary Clinton was dismissive of that proposal, saying single-payer would “never, ever happen."

But the Democratic Party has moved swiftly to the left on health care since the election. Most key 2020 contenders — including Sens. Elizabeth Warren (D-MA), Kirsten Gillibrand (D-NJ), and Corey Booker (D-NJ) — have said they support the idea of single-payer without necessarily backing Sanders’ bill or an existing bill. More than half of House Democrats now support Rep. John Conyers’s (D-MI) single-payer bill — a historic high.

"During Obama's term, Democrats were uncomfortable with anything that might look like something other than full-throated support of the Affordable Care Act, and they didn't want to do anything that might undermine the president," said Dan Riffle, Conyers's senior legislative assistant, in an interview this March. "But many members who weren't on the bill, who have had their phones ringing off the hook, are now expressing interest. It's percolating from the ground up."

Harris’s new support for Sanders’ coming bill helps confirm its status as moving much closer to the Democratic Party mainstream. “It's so much better people have meaningful access to affordable health care at every stage from birth on,” Harris told the crowd. “This is about understanding health care should be a right, and not a privilege.”