Sen. Kamala Harris, a rising star in the Democratic party, is the first in her party to endorse Sen. Bernie Sanders' single payer health bill. Zach Gibson/Getty Images Sen. Kamala Harris, one of the most talked about possibilities for the 2020 presidential race, just became the first Democrat to endorse Sen. Bernie Sanders' single-payer healthcare bill.

Harris broke the news at a town hall in Oakland, California on Wednesday, telling constituents she's supporting the bill because "it's just the right thing to do" and, she added, because it makes fiscal sense.

"It is so much better that people have meaningful access to affordable healthcare at every stage of life, from birth on," Harris said. "Because the alternative is that we as taxpayers otherwise are paying huge amounts of money for them to get their health care in an emergency room. So it's not only about what is morally and ethically right, it also makes sense from a fiscal standpoint, or if you want to talk about it as a return on investment for taxpayers."

Other prominent Democrats — as well as possible presidential candidates — have voiced their support for single-payer healthcare, which Sanders has dubbed "Medicare for all." Sens. Elizabeth Warren and Kirsten Gillibrand have both said that single-payer is the way forward.

Some progressives are saying support for single-payer is the new litmus test for Democrats.

This is a turning point for the party, which, under President Barack Obama's leadership, stopped short of advocating for single-payer, deeming the proposal politically impossible.

Less than two years ago, then-presidential candidate Hillary Clinton said a single-payer system would "never, ever come to pass." Clinton settled on a more moderate proposal — an expanded Medicare system that people could buy into at a younger age.

Sanders, whose supporters have been critical of some of Harris' positions, thanked the junior senator for her support on Twitter on Wednesday night.