In a moment when the most credible left-wing presidential candidate in American history has become the frontrunner for the Democratic nomination, it’s difficult not to feel the absence of the labor movement from the effort. With some noteworthy exceptions — a few left-wing unions and some ideologically committed locals of unions that are neutral on the national level — organized labor has watched the Bernie Sanders campaign, with its acknowledgment of class conflict and its call for working-class victory, from the sidelines.

Now, as Sanders advances, it’s disturbing to see outright opposition emerge from a union with enormous influence in a key state, which has long been known as a beacon of militancy: Local 226 of Unite Here, otherwise known as the Culinary Workers Union of Las Vegas.

The Culinary has constructed in the Sun Belt desert something that seems to belong to another moment in history. It represents 60,000 hospitality workers across Nevada’s casinos, forming an enormous concentration of working-class power in the otherwise hostile territory of the low-wage service economy in a right-to-work state. It accounts for one-fifth of the entire membership of Unite Here, of which it is by far the largest and most internally important local. (The current president of Unite Here, D. Taylor, was previously the president of the Culinary.)

Unite Here’s commitment to building dense, intense, relational organizing networks in its shops has paid off for the Las Vegas working class. Union members bring home wages significantly higher than nonunion equivalents. While hotel work involves significant occupational hazards, union members generally have much more manageable workloads, which reduces their likelihood of injury. They enjoy job security in an industry otherwise characterized by high turnover, and they have protections against sexual harassment and assault for workers vulnerable to predatory guests and bosses.

The union has negotiated for contract language shielding immigrants from ICE raids or termination if their status changes. A union-operated school, the Culinary Academy of Las Vegas, trains thousands of workers every year in new skills to allow them to climb up the occupational ladder. For retirement, there is a defined-benefit pension, not a 401(k). And — jewel in the crown — the Culinary Health Fund provides excellent comprehensive coverage to 139,000 workers and dependents, even operating a health center for members.

Outside of the Chicago Teachers Union, the Culinary probably has been the most widely discussed union local in the country for the last decade — and for good reason. Originally a workplace organizing machine, the Culinary has developed over the last decade into the single most significant force in Nevada politics, deploying huge canvassing armies that have powered Democrats to full control of the state government, taken both US Senate seats, and delivered the swing state consistently for Democratic presidential nominees. Its former political director (and Joe Biden endorser) Yvanna Cancela now sits in the Nevada Senate. Needless to say, it may exercise significant sway in the state’s early caucuses, coming up on February 22.

Unite Here has communicated that it will remain neutral in the presidential race, allowing locals to make their own decisions — and a number, especially in California, have endorsed Sanders. The Culinary, however, has demonstrated growing hostility to Sanders in recent months, apparently because of his campaign’s emphasis on Medicare for All.

In December, the union hosted Sanders for a town hall. There, a worker asked him, “We love our Culinary health care. We want to keep it. We don’t want to change it. Why would you change it?” As Sanders answered, he was interrupted by union members chanting, “Union health care!” (Personally, I find it difficult to imagine that no forethought went into this episode on the part of the union, although I have no evidence of this and Taylor moved to quiet the hecklers down.)

Then last week, the Culinary released a flyer that read, “Some politicians promise . . . ‘You will get more money for wages from the company if you give up Culinary Health Insurance.’ These politicians have never sat at our bargaining table or been on a 24/7, 6 years, 4 months, and 10 days strike line—like we have to make an employer pay for healthcare. We will not hand over our healthcare for promises.”

This criticism does not make sense on its face: nobody is asking union members to hand over their insurance before something else is in place. A vote for Sanders is not a waiver of health insurance, nor would a President Sanders be able to dictate any plan into being. Nonetheless, on February 11, the night of the New Hampshire primary, the Culinary released another flyer, this time explicitly contrasting Sanders to all other candidates for his proposal to “end Culinary Healthcare.” The union also reports that it will be communicating this information out to its members.

An obvious attempt to influence the caucus outcome without risking an actual endorsement — and the union’s sterling reputation for making winners — this move predictably invited criticism online, which the Culinary then very promptly denounced as the “vicious” attack of Bernie Bros. All of Sanders’s rivals promptly announced their solidarity with the union, completing the circuit.

I learned to organize with Unite Here. I spent years developing the capacity in myself — under intense pressure and close guidance — to move others in ways that they, and I, often did not believe possible. After a lot of failure, I eventually got reasonably good at it and started to succeed. It’s easily the most significant political experience of my life, and it’s not overstating to say that I wouldn’t be the person I am without having gone through it.

While it’s not for everyone and often overreaches, the union systematically produces extraordinary organizing talent in its members and staff, leading regularly to seemingly superhuman courage and persistence. A hugely disproportionate number of the best organizers I know have come through Unite Here. On the basis of this organizing culture, which demands the intense involvement of shop-floor leaders and the zealous discipline of staff, Unite Here is growing by about 10,000 members each year — not a tidal wave, but almost unheard-of elsewhere in the private sector.

There are many things one may feel about all this. Surely, though, respect, admiration, inspiration, and even sometimes awe must count among any labor militant’s reaction to the Unite Here record.

This transformative quality coexists in a contradiction with an intensely cautious, instrumental, and sometimes cynical tactical approach. It isn’t all bad — far from it. Hotel housekeepers and banquet staff don’t have much economic leverage on their own. For this reason, the union is constantly looking for other opportunities to exert power over employers, which leads Unite Here to prize its relationships with politicians who will play ball.

In itself, this isn’t necessarily wrong; it’s part of the union’s job. The problem occurs when this habit causes the union to break solidarity with the rest of the working class, as when it endorsed Rahm Emanuel for reelection in Chicago in 2015 — standing against a working-class movement for racial and economic justice, apparently in exchange for a handful of favors.

Now the Culinary has done it again in attempting to sabotage a pro-worker candidate — and more importantly the very idea of health care as a right for all. Those who have fought long and bitter fights — and in many cases sacrificed wage gains — to win high-quality health coverage are perfectly justified in being wary of change. They have every right to ask that candidates take their concerns seriously, as Sanders did months ago in adjusting his program in response to union criticism. His Medicare for All proposal would require unionized firms to reenter federally supervised bargaining to reallocate the savings back to workers. This approach is equal to Elizabeth Warren’s both substantively and in near-term political probability. Both represent political positions, not policy blueprints. Yet Sanders’s plan is represented by the Culinary as significantly more threatening. Culinary’s maneuvering is not a substantive policy critique intended to shape legislation, but a political move designed to wedge apart Sanders’s working-class coalition in Nevada.

The leaflets are transparently part of a backhanded effort to discredit Medicare for All and Sanders with the Culinary’s membership without risking an actual endorsement of someone else. One can imagine two possible angles the union is working here. The first is that a President Sanders will be a friend anyway, because Sanders is the candidate of working-class solidarity as a general principle. So there’s no tactical reason not to rack up some chits with other candidates. The second is that the health plan has been one of the most powerful organizing devices the union has, since it delivers such a tangible difference to its members compared to the wasteland of health injustice all around. If the Culinary can make single-payer toxic in Democratic Party politics, it will count it as a win.

Unions do have a first obligation to their members — that’s the nature of collective bargaining. But these calculations have to be balanced against consciousness of the historical moment and the demands of broader solidarity, which is not just a moral question but a political and strategic one. On these counts, the Culinary is making a serious error.

To decide to help worsen the politics of the health care crisis — to actively portray universal health care as bad for workers — in order to protect the union’s fortress of security demonstrates not only a moral failure of solidarity with the millions of workers outside the walls, but also disastrous shortsightedness. Union density is down to 10 percent — and to 6 percent in the private sector. As we have seen repeatedly over the last century, unions that do not build solidarity outside of their pockets of security will become politically isolated and then vulnerable to employer assault. (We’re not even a decade removed from the Wisconsin debacle.) This is especially likely when health care costs run out of control, which is bound to increase pressure on so-called “Cadillac” plans like the Culinary’s. The plan, in fact, just barely escaped being taxed out of existence once already by Obamacare — a clear sign of its political fragility from which the union has learned all the wrong lessons.

We’ve seen much of this before. Through the 1930s and 1940s, the New Deal seemed bound to pass a universal health plan. But in the late 1940s, the industrial unions — the obvious base for such a program — began to get nervous about its chances. While maintaining their nominal and financial support for the legislative proposals coming out of the left-liberal wing of the New Deal coalition, the United Auto Workers, United Steelworkers, and United Mine Workers set about securing privatized plans for themselves. When Harry Truman’s reform proposal ran into the hard-core opposition of the medical lobby, the union rank and file who had made the New Deal from the bottom up a decade earlier were not there to fight for it. The plan fell apart.

“Health security for some thus precluded the possibility of health security for all,” writes scholar Alan Derickson. As historian Jennifer Klein observes in her book For All These Rights, the gap between the limited pockets of security constructed by organized labor and the rest of the population became a powerful weapon against union members themselves in later years, as they were forced into concessionary bargaining over spiraling health care costs — to bring them back into line with the market. Private health insurance began in a political defeat for organized labor, and then later provided employers a potent weapon to attack unions further.

Today, many of the gleaming hospitals and clinics built in the 1950s to supply privatized health care to steelworkers and coal miners have been sold off or closed down. Many were distressed as soon as the 1970s. Workers protested, but there were too few of them. This, not indefinite security, will be the fate of the Culinary Health Plan without Medicare for All; not in one contract cycle or two, but probably within our time, and certainly sooner than the union seems to think.

The Culinary accuses Medicare for All advocates of asking its members to risk their health care without a guarantee. Solidarity, it’s true, is always a risk. In every union drive, the boss’s anti-union campaign will without fail warn the workers that they don’t know for sure what the union will be able to deliver.

The employer always insinuates that maybe things will get worse — can the union promise they won’t? Why won’t union organizers spell out the specifics of what will be in the contract? Every organizer has had this conversation. The only good answer: we can’t promise anything except that we’ll stick together, and if we do that, we’ll win.

The Culinary is far more a model of working-class solidarity than an enemy, and its members even more so. But its logic on health care politics is the boss’s logic. Its members, and the rest of America’s workers, will have to show we can stick together anyway.