In August of 1964, 14,000 retirees arrived by the busload in Atlantic City. Representing the National Council of Senior Citizens (NCSC), the former railroad workers, dressmakers, and auto assemblers marched 10 blocks up the fabled New Jersey boardwalk to the Democratic National Convention at the Convention Hall. The group, which was organized and bankrolled by the AFL-CIO, moved en masse in floral housecoats and sandwich boards with slogans like “Our Illnesses Burden Our Families” and “Senior Citizens Vote, Remember Medicare.” They intended to push President Johnson to extend public health insurance to millions of Americans.

Astonishingly, lesthey s than a year later, they won. Medicare was signed into law in July of 1965 in Independence, Missouri, at a ceremony attended by former president Harry S. Truman, whose push for national health insurance (NHI) had collapsed nearly two decades before. The landmark law created a public-sector insurance pool for Americans 65 and over, which remains today the closest thing to a robust universal entitlement in the US health-care system. Its successful passage (which also passed Medicaid, to insure the very poor) stands in sharp contrast to multiple failed efforts to install a universal single-payer system.

A half-century later, we’re witnessing the early stages of yet another popular thrust toward single payer, increasingly billed as “Medicare for All.” The nomenclature intends to evoke associations with the popular, trusted program, and is perhaps easier for Americans to latch onto than a phraseology that threatens to trigger a tedious lesson in comparative health policy. But if the conceptual jump from Medicare to Medicare for All can serve as a rough model for achieving universal health care in the United States, we should also look to the history of the social movements that achieved something that then, too, seemed impossible.

No one imagines expanding Medicare to all Americans will be easy. Nothing quite like this has ever been accomplished in the United States. Yes, dozens of peer countries have built coherent, humane, universal health-care systems out of entrenched private ones. Yes, mass movements have won major leftist reforms. Yes, advanced private industries of various nations have been nationalized. But human history offers no examples of these things happening in combination, which is what winning Medicare for All will require.

Other countries’ publicly financed health-care systems were built atop systems far less entrenched and commodified than ours, and therefore presented far less of a threat to capital. The most recently implemented single-payer system was devised in 1995 in Taiwan, a country whose health-care system was underdeveloped after decades of repressive governance followed by decades of mega-growth. The UK’s National Health Service—a fully socialized system of financing and delivery—sprouted from the wreckage of World War II, not high-performing investor-backed hospital chains. And while there are many examples of robust public-entitlement programs’ being privatized, there are few instances of the opposite. This is perhaps why critics such as Hillary Clinton have said that the establishment of single payer in the United States will “never, ever come to pass,” the implication being that it’s not even worth trying.

The most viable push toward NHI in American history crumbled in the late 1940s, ruthlessly crushed by not only insurers and pharmaceutical companies but also the American Medical Association. (Physicians, whose already handsome salaries began to rise in the postwar era, feared the blow that NHI could strike to their paychecks, professional prestige, and autonomy, since a government payer would also reduce their control over prices.) As such, the AMA famously shook down its membership for $25 apiece to fund the multimillion-dollar campaign that injected the phrase “socialized medicine” into mainstream American culture.

In this context, it’s perhaps tempting to view Medicare as a capitulation to industry pressure and political challenges, rather than as evidence they can be flouted. After all, Medicare (and, for that matter, Medicaid) targeted the most vulnerable patients. Many single-payer skeptics insist that Medicare managed to pass because it covered the people private insurance left behind. In his book Harry S. Truman Versus the Medical Lobby: The Genesis of Medicare, historian Monte Poen presents Medicare as a sort of compromise between the unfettered free market and the dashed dreams of the 1940s.

While it’s true that the enactment of Medicare didn’t pose nearly the threat to certain health-care-industry stakeholders that the NHI did or that Medicare for All would, it would be a mistake to fully dismiss its applicability to the current political fight. For one thing, the common talking point that Medicare extended insurance to a population who didn’t have it, rather than squashing existing private infrastructure, doesn’t bear out. A full half of elderly Americans did have private insurance plans when Medicare was signed into law. Commercial health insurers initially opposed the program, and began to support it only when it became clear a large administrative role would be preserved for for-profit insurers.

More importantly, while insurance companies certainly fought against health-care-financing reforms, physicians associations and hospitals are typically considered to have been the more significant opponents—they believed Medicare to be a likely conduit for eventual full-scale single payer (and all the government interference they assumed would come with it), and struck back with more or less the same zeal that they mustered decades earlier. As historian Jill Quadagno puts it, the AMA fought Medicare with “every propaganda tactic it had employed during the Truman era.” Such tactics included a widespread media blitz, advertising in doctors’ offices, and visits to congressmen from physicians in their districts. One tactic, called “Operation Coffee Cup,” deputized physicians’ wives to host ladies’ gatherings, at which they’d play their guests an anti-Medicare PSA starring actor Ronald Reagan.

This time, the AMA and its allies failed, but not for lack of trying. So it’s unfair to ascribe Medicare’s triumph to a lack of industry resistance, which was actually quite strong. The more crucial variable distinguishing Medicare from the NHI battles that fizzled before and since was a mass movement of people demanding it, having coalesced at a moment when powerful liberatory struggles against white supremacy and poverty had transformed what could be deemed politically possible.

Organized labor went all-in for Medicare, which took substantial pressure off unions for their retirees’ mounting health-care costs. Their enthusiasm contrasted with their relationship with universal initiatives before and since, despite their largely supporting most on paper. The reasons for labor’s tepid support for single payer have been debated by historians: For one thing, the unions’ success at collectively bargaining for employer-provided health benefits during the Truman-era reform battles perhaps reduced their motivation to prioritize national health-care solutions, the ongoing absence of which almost certainly highlighted the advantage of union membership. Since the 1970s, ever-rising health-care costs strengthened the case that labor’s interests would be served by removing health-care benefits from tense contract negotiations, but declining labor power during America’s rightward political shift tied them to a Democratic Party establishment unwilling to back single payer during the health-care debates of the 1970s and ’90s.

Today, with a slim majority of congressional Democrats vocally warming up to Medicare for All, and the ACA’s so-called “Cadillac Tax” poised to hit hard-won union-bargained health plans, the pro-labor case for single payer has never been more obvious. Indeed, each of the high-profile wildcat teachers’ strikes widely cited health-care benefits as a central demand. While the AFL-CIO has endorsed single payer, the question of whether workers will rally around Medicare for All the way they did for its namesake could well depend on how the movement’s stakeholders deal with those who stand to be displaced by the streamlining effect of large-scale reform.

But beyond institutional heft or the weight of its endorsements, the most impactful contribution organized labor made to the Medicare fight was a committed army of thousands of boots on the ground, many of them seniors who stood to benefit from the legislation or the family members who worried about how they’d care for them. Even the most precursory survey of 20th-century universal-health-care movements makes their most egregious failure stunningly obvious: They were nearly all top-down operations practically devoid of participation of ordinary people intent on changing the status quo.

By the time the NCSC marched in Atlantic City, this movement was already years in the making. It had been building momentum for the idea that would become Medicare in the 1950s, under a Republican president who, in is 1954 State of the Union address, had affirmed he was “flatly opposed to the socialization of medicine.” Rather than standing by waiting for better electoral luck, the Medicare movement fought to make theirs a winning campaign issue that would help to elect Democrats, not the other way around.

For years, the NCSC spearheaded letter-writing campaigns targeting media outlets and elected officials, and did any media outreach it could. It churned out brochures to counter the messaging of the powerful medical lobby, printing and distributing millions of pamphlets and fliers. As Blue Carstenson, then head of the NCSC, recounted later, “We had to make it a cause and we made it a cause…. We charged the atmosphere like a campaign…. We were always jammed in there and there was a hustle and bustle atmosphere. And when reporters came over they were always impressed by telephones ringing and the wild confusion and this little bitty outfit here that was tackling the whole AMA in a little apartment on Capitol Hill…. This was news. It used to make every reporter chuckle or smile.”

So too did the NCSC learn to push the buttons of electoral politics: It organized groups to testify before Congress about insurance premiums, which rose as much as 35 percent some years, like some ACA marketplace plans. And of course, Carstenson’s formidable elderly army turned out to campaign events. When Democrat George Smathers declined to support Medicare before the 1964 election, NCSC members organized town-hall meetings throughout the state—including one in Fort Lauderdale that was allegedly so successful that the organizers had to upgrade to a bigger venue three different times. Their message made appeals to all ages: Relief for seniors’ medical costs, they argued, will also reduce financial pressure on their working-age children, who’d in turn have more room in the budget to raise their own kids.

If the participants in today’s movement for Medicare for All intend to succeed, they must preempt the imminent counterattack of a health-care industry with far more fortunes at stake than the one their counterparts vanquished in 1965. This will require a mass mobilization of people making themselves seen and heard, whose demands for universal public insurance must reach a fever pitch to force candidates and current officials to capitulate. Doing so will demand a broad variety of tactics, including direct action, canvassing, printed materials, and public events, geared toward not only  persuading regular voters but also inspiring new ones.

Finally, this vision of justice must extend beyond the realm of health care alone. It is nearly impossible to imagine Medicare passing outside the political context set forth by the civil-rights movement, and the so-called War on Poverty. These years-long mobilizations of oppressed people had forced the political reckoning that fostered large-scale reform. It is no coincidence that the New Deal and the Great Society—however short they may have fallen—came about in large bursts rather than undetectable spurts.

Paradigm-shifting reforms have been delivered by broad coalitions confronting a common enemy. It’s up to advocates to compel people living under the US health-care system to see themselves and one another as part of a single constituency, from the poorest uninsured to those saddled with punishing paperwork, office staff chained to bad jobs for benefits, providers-turned-pawns of corporate conglomerates, and expectant mothers bracing themselves for exorbitant out-of-pocket costs atop weeks of unpaid maternity leave. And it must be done in solidarity with struggles on behalf of all oppressed Americans—people of color, the unhoused, the disabled, and others—whose subjugation benefits the very moneyed interests who’d prefer to keep things as they are.

All the evidence tells us that robust universal programs build solidarity, and create an impassioned base that enthusiastically defends them. Once Medicare for All is in place we can expect the same. Until then, it’s up to advocates to compel as many people as possible to envision the radically different society that stands to inherit it—and to accept nothing less.