Last month, Democrats achieved an historic win in New York, flipping control of the state senate and thus taking control of the entire government, upending a weird status quo during which a group of breakaway Democrats allowed the Republicans to control the legislature's upper chamber. Now that they actually have the power to pass laws in one of the most Democratic states in the country, the possibilities seem intoxicating for the left: Abortion access could be codified into law, the subways could finally be fixed, the state's byzantine election laws could be updated, and New York could commit to fighting climate change.

But right near the top of any progressive wish list is the New York Health Act, the state's version of Medicare for all—which is to say universal, government-provided—health insurance. Single-payer healthcare, as such systems are also called, has been a left-wing lodestar for generations. If the NYHA passed, it would make New York the first state in the union to guarantee free access to healthcare (and freedom from fear of health-related bankruptcy) to all of its residents, including undocumented people.

If passed and smoothly implemented, NYHA could be not just a way to improve the lives of New Yorkers but a model for the rest of the country as it debates the merits of Medicare for all, a policy backed by Bernie Sanders and many other potential 2020 presidential contenders. But now that Democrats can actually pass the NYHA, single-payer supporters are facing a fight that could pit them against not just the insurance industry but a host of Democratic constituencies and leaders—a preview of the contentious debate over healthcare that might follow victories in 2020.

The foremost obstacle is the powerful medical industry lobby, which will likely deploy the usual counterattacks—think the "death panels" of the Affordable Care Act debate, or the fear-mongering "Harry and Louise" ads that helped scuttle reform in the 90s. Then you have Democratic lawmakers who may hesitate to back a transformative proposal that would raise taxes on a lot of people, a governor who doesn't seem particularly warm to the idea, a hostile federal government, and potential lawsuits from employers. While the coming NYHA battle represents a possible turning point in the history of healthcare politics, it won't be a pretty sight.

Yet if single-payer advocates could get past all that, they'd have a roadmap to victory in other states—and a model that could be replicated in DC.

Richard Gottfried, the chair of the New York State Assembly's Health Committee and the chief architect of the NYHA, recently explained what it would look like. "It would create universal complete health coverage for every New York resident without premiums, deductibles, copays, or restricted provider networks," he said over the phone. The bill would pay for this by pooling the money the state gets from the federal government for programs like Medicaid and Medicare, and also by raising taxes. "There would be one tax on payroll income, predominantly paid by employers, and a parallel on unearned income like dividends, capital gains," Gottfried explained.

This would transform the way New Yorkers pay for healthcare—instead of giving premiums to insurers, they'd be getting taxed—and according to a recent study by the RAND Corporation, overall health spending would drop by $80 billion, or 2 percent, by 2031, even as the roughly 1.2 million currently uninsured New Yorkers gained access to care. Gottfried said he didn't necessarily agree with RAND's report (for one thing, his bill as currently written does not specify tax rates, so RAND analysts made assumptions about what those rates would be) but NYHA backers have trumpeted the finding that the bill could drive costs down.

The arguments against the NYHA are echoes of the normal arguments marshaled against single-payer healthcare. Realities of Single Payer, an anti-NYHA organization made up mostly of business and health insurance interests, warns of high taxes, long wait times for care under a government-run system, and job loss in the insurance industry. (Through a spokesperson, Realities of Single Payer said in a statement that "rather than throwing out a functioning system for a very uncertain future, there should be a greater focus on covering the remaining uninsured New Yorkers.") Katie Robbins, the director of Campaign for New York Health, a coalition of unions, doctors, and left-leaning groups, called these warnings "talking points that are used to create fear" and noted that this year's election proved single-payer was popular statewide.

"There's been a longtime narrative, a false narrative in my opinion, that this is an issue that only New York City liberals care about," Robbins said. "But what we saw reflected in the results is that Senate candidates outside of New York City—Long Island, Hudson Valley, upstate in Syracuse—who ran on the New York Health Act, not just standing on it, but making it a priority of their campaign... handily won their elections."

Those election results create pressure on Democrats, according to Hank Sheinkopf, a longtime Democratic consultant in the state who has worked for everyone from Andrew Cuomo to Michael Bloomberg to Bill Clinton: "They have to do something."

The NYHA—which Gottfried has introduced into the Assembly every year since 1992—has passed the lower legislative chamber in each of the past four years. But even with increased support in the Senate, its path to becoming law is tricky to say the least. The top Democrat in the State Senate, Andrea Stewart-Cousins, seemingly embraced the NYHA last year, but after the election said Democrats wouldn't raise taxes. And while Governor Andrew Cuomo said the NYHA was a good idea "in theory" during a debate against his left-wing primary challenger Cynthia Nixon, he was also skeptical of the cost and said he'd like to see single-payer healthcare be implemented on a federal, rather than state, level. (Neither Stewart Cousins nor Cuomo responded to requests for comment left with their offices.)

Meanwhile, unions remain a powerful force in state politics—especially in New York City—and some might oppose the NYHA because members generally have good insurance they won through negotiations and may not want to replace that with government-provided plans. Other barriers include the Trump administration potentially refusing to grant waivers to New York that some say would be necessary for the plan to be implemented (Gottfried disputed that such waivers would be needed) and potential lawsuits from employers under a federal statute called ERISA that protects employers who choose to pay insurance claims themselves.

It's also not even clear the NYHA will pass the Assembly when the legislature goes back into session in January. "It's like starting from scratch because the political dynamics changed so much," Robbins said. In other words, now that everyone knows the NYHA may actually become law, some Democrats may have second thoughts about voting for it.

Gottfried, for one, seemed confident of the bill's chances. "I fully expect the Assembly to pass the bill again," he said. He added that he and NYHA Senate sponsor Gustavo Rivera were talking to stakeholders to flesh out the details of the bill and add "additional provisions" to speed its passage through the Senate. They were also "working to convince" Cuomo that the NYHA was the way to go, Gottfried said.

If Gottfried and his allies can pass the legislation quickly in early 2019, it will put Cuomo on the spot, former Assembly member Richard Brodsky—a frequent Cuomo critic—argued in a recent Albany Times-Union column: "Anything short of immediate support puts him under the same kind of statewide and national pressure, intensified by any presidential ambitions he may have." It's safe to say that reticence on Cuomo's part will spark widespread progressive anger. “If Andrew Cuomo’s first appearance in 2019 is to put a bullet through the head of single-payer, it will have political consequences,” Brodsky said in an interview.

If the dynamics of passing the NYHA seem complicated, welcome to a preview of what national politics may look like in 2021. If Democrats can retake control of the federal government in the 2020 elections, they will have likely done so while promising single-payer healthcare, just as New York Democrats did. But passing a bill through Congress will require selling it to voters in the face of intense opposition from insurance companies and the medical industry, and also navigating the push and pull of other priorities like climate change. Medicare for all can seem like a common-sense solution to the country's patchwork, inhumane, and overpriced healthcare system when advocates talk about it, and it's popular in many polls. But history suggests the politics turn thorny when government-provided health insurance becomes a real possibility.

“You’re treading into unknown territory here. There’s no map for how to get this down the road."

–Richard Brodsky

Recent single-payer pushes have come tantalizingly close in other states, only to fail, sometimes in dramatic fashion. In 2014, Vermont Governor Peter Shumlin pulled the plug on a single-payer bill, saying his state couldn't pay for it. Two years later, a Colorado ballot measure that would have created a single-payer system was rejected by voters after a confusing election-season scrum—abortion-rights groups opposed the measure because the new system wouldn't have covered such procedures. Last year, a California single-payer bill was effectively axed by Assembly Speaker Anthony Rendon, who said it was "woefully incomplete" and didn't describe how the system would be paid for. (Single-payer advocates were so incensed they subsequently attempted to remove Rendon from office.)

Gottfried said that unlike the California bill, the NYHA clearly describes where the funding would come from, and unlike Vermont, New York has enough wealth to make paying for a single-system more practical. But other Democratic factions, including some unions and the governor, may not be persuaded by those arguments, setting up a fight between single-payer advocates and the rest of the party, with lawmakers caught in the middle.

As Robbins pointed out, six of the eight former members of the Independent Democratic Caucus—the rogue Democrats who gave control of the Senate to Republicans—lost primaries to grassroots opponents earlier this year, indicating the same base that is demanding single-payer has some teeth. "I would think that the folks who are in elected office now should really figure out how to deliver what they promised in their campaigns," she said, "because clearly there is a motivated base with high expectations and now the electoral muscle to make them pay at the polls if they don't deliver."

That said, Robbins added that "there's absolutely no guarantee" the bill will pass, and a lot could depend on pressure from activists. Brodsky suggested NYHA sponsors consider a "toned down" bill that is less costly and helps manage the transition so as to address criticisms about job losses in healthcare. He also said Gottfried had the “political shrewdness” to get it done.

“You’re treading into unknown territory here. There’s no map for how to get this down the road. It’s an enormous challenge," Brodsky said, adding, "the political climate has changed from roughly unfavorable to roughly favorable. That’s not chopped liver.”

The battle over the NYHA will be a state-level political knife fight, but the stakes could be even higher than the future of healthcare in New York. The hope among advocates is that once a single-payer system gets a foothold in one state, it can be exported around the country. The passage of the NYHA would not be the end point of the movement, but the beginning of a new chapter.

"Social progress in this country historically, usually begins at the state level," Gottfried said. "Our labor laws, a lot of our consumer protection laws, public support for healthcare for poor people, the child health insurance program—all began at the state level."

Update: After publication we received a comment from Realities of Single Payer. This piece has been updated to include that comment.