Over the past year, the Demo­c­ra­t­ic Par­ty has under­gone a mon­u­men­tal shift left on the issue of health­care. Today, Bernie Sanders intro­duced his Medicare for All bill with the sup­port of 15 co-spon­sors in the Sen­ate — a third of the Demo­c­ra­t­ic cau­cus. In 2013, the last time Sanders intro­duced such a bill, it had just one spon­sor: himself.

Leading Democrats are now on the record backing revolutionary change in the American healthcare system that would remove both the private insurance industry and financial barriers to accessing care—finally enshrining healthcare as a right.

A new polit­i­cal con­sen­sus is form­ing around an idea that as recent­ly as last year seemed anath­e­ma to main­stream Demo­c­ra­t­ic offi­cials. Democ­rats at all lev­els of pow­er now face the choice of join­ing the cho­rus demand­ing uni­ver­sal, decom­mod­i­fied health­care, or being left behind.

Sin­gle payer’s rapid growth in insti­tu­tion­al sup­port is a tes­ta­ment to the ded­i­cat­ed work of sin­gle-pay­er advo­cates across the coun­try who’ve orga­nized in the face of a GOP-led gov­ern­ment that would rather strip health insur­ance from mil­lions of Americans.

Sanders has used his new­found lead­er­ship posi­tion in the Demo­c­ra­t­ic Par­ty to coa­lesce par­ty lead­ers and up-and-com­ers in the Sen­ate around an issue that was a cen­ter­piece of his 2016 pres­i­den­tial cam­paign — one that Hillary Clin­ton infa­mous­ly said would ​“nev­er, ever come to pass.”

In addi­tion to long­time vocal sin­gle pay­er sup­port­ers such as Jeff Merkley and Bri­an Schatz, the bill’s spon­sors also include Cory Book­er, Kamala Har­ris, Kris­ten Gilli­brand, Al Franken and Eliz­a­beth War­ren — all fig­ures with grow­ing pop­u­lar­i­ty in the par­ty who are fre­quent­ly float­ed as poten­tial 2020 pres­i­den­tial contenders.

The bill is also spon­sored by Wisconsin’s Tam­my Bald­win who rep­re­sents a state that went for Bernie Sanders in the pri­ma­ry but flipped red in the gen­er­al to go nar­row­ly for Don­ald Trump. Even for­mer Mon­tana Sen. Max Bau­cus who is cred­it­ed with cra­ter­ing the sin­gle-pay­er push dur­ing Oba­macare nego­ti­a­tions in 2010 now says of sin­gle pay­er, ​“It’s going to happen.”

So how did the tide turn in sup­port of sin­gle-pay­er? Sanders didn’t hit some wonk­ish pol­i­cy sweet spot where the num­bers final­ly added up and the tech­nocrats gave their seal of approval. Rather, over the course of Sanders’ pres­i­den­tial run and through­out the recent GOP-led efforts to over­turn Oba­macare, pub­lic sup­port for a Medicare for All sys­tem didn’t just grow — it trans­lat­ed into real polit­i­cal pressure.

Sanders cham­pi­oned sin­gle pay­er every chance he got through­out the pri­ma­ry — on TV appear­ances and at his mass ral­lies. This past spring and sum­mer, con­gres­sion­al town halls were jam-packed with con­stituents demand­ing a health insur­ance sys­tem that would pro­vide them with the care and the drugs they need to sur­vive with­out dri­ving them into bankruptcy.

Groups such as Nation­al Nurs­es Unit­ed, Physi­cians for a Nation­al Health Pro­gram, Health­care Now!, Our Rev­o­lu­tion, Jus­tice Democ­rats and the Demo­c­ra­t­ic Social­ists of Amer­i­ca ener­gized their mem­ber­ship to knock doors, peti­tion rep­re­sen­ta­tives and build pub­lic sup­port behind single-payer.

Mean­while, advo­cates for sin­gle pay­er have fol­lowed Sanders’ lead in mak­ing the moral case for a uni­ver­sal health­care sys­tem in the Unit­ed States. Rather than focus­ing on the need to bring down health­care costs to cut the deficit, sup­port­ers have reject­ed the vocab­u­lary of aus­ter­i­ty and instead called upon the need for a humane and just sys­tem that doesn’t dis­crim­i­nate based on eco­nom­ic stature.

The approach was on full dis­play dur­ing a MSNBC-host­ed town hall event with Sanders in McDow­ell Coun­ty, W.Va., in March. McDow­ell, a for­mer min­ing com­mu­ni­ty, is one of the poor­est areas in the state and was won by Don­ald Trump in 2016 with 75 per­cent of the vote.

Speak­ing to a crowd of McDow­ell res­i­dents and Phil, a for­mer coal min­er who vot­ed for Trump, Sanders said:

“What I am going to tell you is not utopi­an, it’s not crazy, it is real. For a start, health­care must be a right of all peo­ple, work­ers and retirees.

“Let me pose this ques­tion to Phil and to oth­er peo­ple. We are the only major coun­try on Earth, the only one that doesn’t guar­an­tee health­care to all peo­ple as a right. What do you think? Do you think we should join oth­er coun­tries and guar­an­tee health­care as a right of all people?”

Phil replied: ​“Yeah. I think every Amer­i­can cit­i­zen should have healthcare.”

It turns out that Phil is not alone. This strat­e­gy of mak­ing the moral case for uni­ver­sal health­care has paid off. Polls show Amer­i­cans increas­ing­ly sup­port a Medicare for All sys­tem. A recent Kaiser poll put pub­lic back­ing at 57 per­cent. And in an April Economist/​YouGov poll, 60 per­cent said they want to ​“expand Medicare to pro­vide health insur­ance to every American.”

As the wide­spread sup­port for Sanders’ bill shows, this mes­sage is begin­ning to make its way into the halls of pow­er in the Demo­c­ra­t­ic Par­ty. Lead­ing Democ­rats are now on the record back­ing rev­o­lu­tion­ary change in the Amer­i­can health­care sys­tem that would remove both the pri­vate insur­ance indus­try and finan­cial bar­ri­ers to access­ing care — final­ly enshrin­ing health­care as a right.

But this does not mean that Medicare for All won’t face stark oppo­si­tion from forces inside the Demo­c­ra­t­ic estab­lish­ment. It’s notable that mem­bers of par­ty lead­er­ship — Chuck Schumer, Nan­cy Pelosi and Ste­ny Hoy­er — have all refused to pub­licly back Sanders’ bill, as has Demo­c­ra­t­ic Nation­al Com­mit­tee Chair Tom Perez.

These and oth­er Democ­rats may be wary of sign­ing onto a pro­gram that Repub­li­cans could for once accu­rate­ly attack as social­ized health insurance.

Yet in oppos­ing Medicare for All, these Democ­rats will be sid­ing with the insur­ance indus­try, phar­ma­ceu­ti­cal com­pa­nies and Wall Street investors that ben­e­fit from the cur­rent sys­tem — a sys­tem which leaves tens of mil­lions of Amer­i­cans with­out insur­ance while fill­ing cor­po­rate cof­fers with bil­lions in profits.

Sanders, writ­ing in a New York Times op-ed today, said that these oppo­nents of sin­gle pay­er are ​“on the wrong side of history.”

By build­ing a con­sen­sus around Medicare for All, Sanders and oth­er advo­cates have cho­sen a side in a bat­tle that affects much more than just healthcare.

On issue after issue, from rais­ing the min­i­mum wage and pro­vid­ing paid fam­i­ly leave to chal­leng­ing mass incar­cer­a­tion and end­ing dis­crim­i­na­to­ry hous­ing prac­tices, this fight against cor­po­rate inter­ests and the mem­bers of Con­gress who rep­re­sent those inter­ests will be cen­tral to achiev­ing pro­gres­sive polit­i­cal goals.

It’s heart­en­ing to see that a third of the Democ­rats in the Sen­ate have now signed onto this fight by back­ing Sanders’ bill. It’s now up to the rest of the Demo­c­ra­t­ic estab­lish­ment to show which side they are on.