Democrats and Republicans have always had dramatically different ideas about health insurance and health care and what the proper role of government would be in guaranteeing (or not) that every American has access to both.

But those differences have perhaps never been as obvious as they were this year — when Republicans strived and failed to overturn the Affordable Care Act while single-payer went mainstream among Democrats.

Little changed on the ground: Nearly as many people signed up for ACA coverage in 2017 as in 2016, despite the Trump administration’s efforts to undermine enrollment. Obamacare’s Medicaid expansion remains in effect. And while Republicans managed to eliminate Obamacare’s individual mandate in their tax bill, most health policy experts believe the law should largely continue to function, if imperfectly.

Yet 2017 felt like health care was balancing on a precipice. On one side was deregulated health care, without the protections or guarantees or assistance provided by the ACA. On the other was a single, government-run program that provides health insurance to every person.

The starkness of the choice could make 2017 a turning point in health policy. Twice before — in 1981 and 1995 — a dramatic Medicaid overhaul seemed like a possibility. But this year seemed even more significant, Sara Rosenbaum, a George Washington University professor who has been following health care policy since the 1970s, told me.

“Here we have both the starkness of Medicaid differences and the enormous philosophical differences in what should be the national approach to the regulation and subsidization of insurance markets,” she said. “We have gone from a fairer and more equitable vision of private insurance stability to one where the only role for the federal government is to subsidize an enormously costly high-risk pool — poorly.”

“Tremendously different views,” she said.

Republicans fought to dramatically shrink the government’s health care role

Repealing Obamacare, which had covered upward of 25 million Americans and extended ironclad protections for people with costly medical histories, was the top priority for Republicans after Trump’s victory. They set out to keep their campaign promises of the past eight years, when they swore to uproot the ACA root and branch.

Republicans didn’t know exactly what they wanted to do, but they did know they wanted to significantly shrink the role of the federal government. Their attack focused on three fronts:

Repealing the health care law’s mandates, particularly the requirement that every American have insurance or pay a penalty. Republicans viewed the individual mandate as a grotesque overreach of government authority.

Deregulating the insurance market, whether by totally undoing Obamacare’s rules prohibiting insurers from denying people coverage or charging them higher premiums based on their medical history, or by more targeted changes, like relaxing the rules that limit how much more insurers can charge older people than younger people. The GOP argued those regulations have driven up the cost of insurance.

Overhauling Medicaid. In the 30-plus states that agreed to do so, the ACA expanded Medicaid eligibility to every American in or near poverty, making it a universal safety net. Republicans wanted to not only undo that historic expansion of the program but also fundamentally change it by instituting a federal spending cap.

By the end, the Republican desire to get the federal government out of health care, and the lack of agreement on any other details, nearly reached self-parody: The last plan put forward by Sens. Lindsey Graham and Bill Cassidy would have kept much of the ACA’s taxes and spending while merely devolving the policymaking down to the states.

Almost every iteration of the Republican proposal would have led to millions fewer Americans having health insurance. Even so-called “skinny” repeal, which undid the mandates and little else, would have reduced the number of insured by 16 million compared to Obamacare, according to the Congressional Budget Office. The GOP was also confronted with the reality that most Americans support the ACA’s protections for preexisting conditions. That limited their ability to deregulate the insurance market as much as they would have liked and forced them to come up with alternative proposals for covering high-cost patients.

Republicans on Capitol Hill often sought to duck these problems by simply denying that they existed. They would promise that no one would lose coverage, or even that more people would be covered, and their plan’s protections for preexisting conditions were as rock-solid as the ACA.

In my months covering the health care debate on Capitol Hill, Sen. Ted Cruz (R-TX) was one of the few Republicans to mount an intellectually honest defense of how he wanted to change American health care. Cruz proposed allowing plans that did not comply with Obamacare’s rules back on the market, allowing healthier people to buy those lower-cost plans, and the federal government could pick up the tab for people with higher costs as premiums for Obamacare plans rose:

It’s not fair to a working-class person who’s struggling to put food on the table, for the federal government to double their premiums trying to work an indirect subsidy for others who are ill. Far better to have it through direct tax revenue. ... If those with seriously illnesses are going to be subsidized, and there is widespread agreement in Congress that they are going to be subsidized, I think far better for that to happen from direct tax revenue rather than forcing a bunch of other people to pay much higher premiums.

(The problem, as experts told me at the time, was that costs in the Obamacare markets would skyrocket as healthier people migrated to the non-ACA plans, requiring an open-ended federal commitment to cover the rising prices, one that was unlikely to be kept indefinitely.)

It was, at least, honest: Get the government out of health care as much as possible, leaving it to cover only the sickest people who couldn’t otherwise afford coverage. It still would have represented an about-face from Obamacare’s aspiration of universal (or near-universal) coverage.

But in the end, Republicans faced three problems they couldn’t overcome. Enough senators were dissatisfied with their plans for undoing Obamacare too much (Sens. Collins and Murkowski), for not doing enough (Sen. Rand Paul), or for the haphazard process that produced these proposals (Sen. John McCain).

Obamacare, for all of its flaws, proved too resilient to repeal. Even with the blows leveled by the Trump administration and the repeal of the individual mandate in the GOP tax bill, the law survived 2017 and should continue to survive.

But the GOP had outlined its vision for health care more clearly than it ever had in the preceding years, when the party had put forward little more than its vague promise to “repeal and replace” the health care law.

Democrats are now dreaming of a government-run health care system

In the fall, Sen. Bernie Sanders (I-VT) put out his most detailed plan yet for Medicare-for-all. The bill called for every American to be covered by a government insurance program. Almost all of their health care, with the exception of some prescription drugs, would be free to them when they went to the doctor’s office or the hospital. It would be, as Vox’s Sarah Kliff explained earlier, even more generous than the universal health care programs in European countries.

It would presumably be paid for through higher taxes, some on the rich but some surely borne by the middle and lower classes, though they would no longer have to pay insurance premiums or most out-of-pocket costs. Sanders decided to leave this part of his plan, the trickiest issue in the political debate that would come, the most undefined.

But as notable as the details in Sanders’s proposal were, equally important were the other Democrats he attracted to support it. A few years ago, Sanders would introduce a single-payer bill all on his own. In 2017, he won the support of Sens. Kirsten Gillibrand (D-NY), Kamala Harris (D-CA), and Cory Booker (D-NJ), the presumed frontrunners in the Democratic race to challenge Trump in 2020.

In the debate over whether health care should be a right, the left is winning, at least within the progressive party.

“Health care should be a right, it should not be a privilege, once and for all,” Gillibrand said when the plan was announced. “So I’m standing with Bernie and I hope all of you, to make sure that every single American gets access to affordable, high-quality health care with a single-payer system in America.”

Among Democratic voters, single-payer is now the majority position.

The American public is trending that way too. The public’s perception of the government’s role in health care took a hit after the sharply divisive debate over the ACA, but reemerged as strong as it’s been in years during the great health care debate of 2017.

Health policy historians and polling experts caution against reading too much into those numbers. The public has not yet been subjected to a detailed, granular debate about switching to a single-payer system. There are real trade-offs that would emerge if and when that debate comes. Americans might like the sound of guaranteed health coverage, but they’re also historically uncomfortable with the government taking too big a role in our lives.

The trend lines, nevertheless, are clear. Some Republicans are hoping to revisit their more ambitious Obamacare repeal plans next year, and if House Speaker Paul Ryan has his way, Medicaid and Medicare would be subjected to dramatic overhauls that scale back the federal government’s role and transition more responsibility for them to the states and the private market. Democrats, meanwhile, have their sights set on a more inclusive Medicare program — whether through Medicare-for-all or a more targeted expansion of a Medicare buy-in, like the one proposed by Sens. Tim Kaine (D-VA) and Michael Bennet (D-CO).

Paul Starr, a Princeton University professor who is the foremost expert on the history of American health care, emphasized that health care has always been a polarizing issue. In one sense, nothing has really changed. But he allowed that the trend lines of recent years have been toward even deeper polarization.

“It is more polarized than it was in the late 1990s, when Democrats and Republicans were at least able to agree on CHIP [the Children’s Health Insurance Program]. And while Democrats didn't like the structure of George W. Bush's Medicare prescription drug benefit in 2003, they agreed with the aim of providing insurance to seniors for drug costs,” he told me in an email. “Then the Romney reforms in Massachusetts in 2006 gave what proved to be a false hope of bipartisanship on health policy at the national level. If you trace the origins of the ideas in the ACA, it was basically a bipartisan bill passed on strictly partisan lines.”

“So, the recent arc over the past 20 years,” he continued, “fits the picture you suggest.”

Any hopes for a grand bipartisan bargain on health care look further away than ever after 2017. Instead, the parties are taking up the issue, now one of the defining points of debate in American politics, and sprinting in opposite directions.