This article was originally posted as part of ThinkWell WPP Health Practice available here.

It wasn’t that long ago that supporters of Medicare for All were a pretty lonely group. I should know. I wrote the Medicare for All bill for Senator Kennedy in 2005. We didn’t get a single co-sponsor in the Senate and Chairman Dingell wasn’t exactly mobbed by co-sponsors either as he introduced the bill in the House. Of course, we weren’t completely alone, as many activists and health policy experts had long spoken in favor of making Medicare available to all Americans, and others had introduced different single-payer plans, but there was virtually no momentum in Congress toward a Medicare for All approach.

Fast forward to 2018 and the picture could hardly be more changed. Medicare for All has become central to the campaigns of many Democrats, from Senator Bernie Sanders to many of the new members elected in the recent midterms, a group that is younger, more diverse and often more liberal than those elected in previous years. Rather than being queried if they do support Medicare for All, Democrats are increasingly being questioned sharply if they don’t.

How has the idea transformed from quasi-taboo to mainstream?

Many factors have led to that transformation—from rising costs to the increased polarization of American politics—but I would single out one as crucial: ever-mounting frustration with the healthcare system and with the politics of healthcare.

A few years after drafting Medicare for All, I helped write the Affordable Care Act. In contrast to the Medicare for All bill of 2005, which went through only a few drafts, the ACA was worked and reworked countless times as we navigated the peril-strewn path toward Congressional approval. While Medicare for All—at least in its more transformative forms—would be a marked shift away from our current healthcare system, the ACA deliberately tried to reform and improve the current system rather than replacing it.

The ACA built coverage options for low-income Americans through heavily federally financed expansions of Medicaid, created new marketplaces for healthcare and disallowed the practice of redlining Americans from health coverage because they had preexisting conditions. In doing so, it didn’t do away with employer-sponsored coverage, private payers or other structural mechanisms through which Americans get care. Instead, it built on existing structures and even threw in a lot of ideas that had been Republican at one point—not least the individual mandate. While some members of Congress had hoped for a Medicare for All bill, or even the more modest public option within the ACA, the votes weren’t there for either of these approaches to pass. Despite taking what I would characterize as a moderate approach, the ACA was attacked by conservatives as a radical plan that represented rampant socialism. Actual socialists, on the other hand, often viewed the ACA as tepid incrementalism. In the nearly nine years since enactment, the ACA has withstood challenges in the Supreme Court, repeal votes in Congress and protests in the street, and remains a lightning rod of controversy—although even many of the most conservative members of Congress have started to portray themselves as defenders of preexisting condition protections, another idea that was once seen as radical but has now become accepted wisdom.

Despite significant progress in expanding coverage and reducing the rate of healthcare inflation, it remains true that not all Americans are covered and that healthcare is unaffordable for many. This combination has convinced many liberals that the right course is not merely to reform the current healthcare system but to remake it through a single-payer version of Medicare for All. After all, they may reason, the backlash against Medicare for All could hardly be more severe than that against the ACA, but at least a single-payer Medicare for All plan would achieve the long-held goal of truly universal coverage and cost savings.

While Medicare for All has completed some of the journey from taboo to acceptance, it still has some way to go. Medicare for All would gore more sacred cows than did the ACA—and many of those cows have sharp horns.

With divided government, the next two years will see little legislative movement on Medicare for All, but it will become a central part of the health debate, the subject of hearings, town hall meetings, online discussions and no doubt a presidential tweet or two. Medicare for All is likely to become a central theme in the Democratic primaries and, depending on who emerges from those primaries, may become a key part of the presidential debate of 2020. That’s a remarkable journey for a bill that couldn’t get a co-sponsor 13 years ago and speaks to the power of healthcare to move opinions, ignite passion and drive people to action.