On paper, the Culinary Workers Union and Sen. Bernie Sanders (I-Vt.) look like a perfect match. The powerful Las Vegas-based local of Unite Here represents service workers throughout the city, making it one of the few places in the U.S. where housekeepers, busboys and cocktail waitresses can lead middle-class lives. Sanders is arguably the most pro-labor presidential candidate to wage a viable campaign in generations. The way the Culinary’s organizing muscle has lifted up the Strip’s most vulnerable workers could make for an entire Sanders stump speech.

But the Culinary has been making Sanders seem a little scary. According to the Nevada Independent, the union recently posted flyers inside employee areas of casinos and hotels warning that Sanders would end the Culinary’s health care program if elected, through his Medicare for All proposal. The message could potentially damage the front-runner in the upcoming Nevada caucuses on Feb. 22, since the union has tremendous reach through its 60,000 members and their families.

It might seem odd to undermine the candidate who’s been walking picket lines for decades and stumped for a $15 minimum wage before anyone else, but the Culinary’s warning to members on Medicare for All isn’t surprising. The union, which is made up mostly of women and Latino members, has built up a health care program that’s the envy not only of low-wage service workers but even well-paid professionals with run-of-the-mill employer coverage. It doesn’t want a single-payer plan like the one Sanders proposes to end the private insurance plan it has built through years of organizing, bargaining and striking.

Union officials would have their own reasons for wanting to keep the current system ― it is, after all, one of the sweetest benefits Culinary membership can offer. (Nevada is a right-to-work state, so unions there must constantly prove their value if the workers they represent are to choose to pay dues.) But plenty of rank-and-file members would share the same concern. When HuffPost was reporting on the Culinary for a 2018 profile of the union’s success, many workers pointed to their excellent health benefits as a point of pride.

Since the whole political world will now be watching whether @Culinary226 endorses someone in Nevada, which would be a genuine earthquake, here’s the candidate policy explainer they’ve sent to members: pic.twitter.com/X3Cgvr3YAX — Matt Pearce 🦅 (@mattdpearce) February 12, 2020

A housekeeper at the Paris resort said that maintaining the current health care coverage was her top priority as the union headed into a new round of negotiations with the casinos. A cocktail server remarked: “My main thing through all this is my health insurance.”

It’s not hard to see why. The Culinary Health Fund is a multi-employer, nonprofit plan that all the employers under the union’s contracts chip into. The fund bills itself as the most generous in Southern Nevada. It provides mental, dental and prescription drug coverage to 139,000 workers and their relatives. The family coverage comes with no monthly premium for workers, unlike most people with plans through their employers. (Sanders’ Medicare for All plan, it’s worth noting, would come with no co-pays or deductibles as proposed.) A few years ago, the fund even built its own standalone health clinic for members, offering adult, pediatric and urgent care onsite. The fund also runs two pharmacies.

The Culinary is arguably the most powerful union local in the country, having organized all but a handful of casinos and hotels on the Strip, and it offers top-notch health care because that’s where it’s chosen to put so much of its leverage. In contract negotiations, wages and health care represent different pockets of the same coat, with employers willing to raise their total labor costs only so much. Culinary members have forgone pay increases in order to create and maintain their prize health plan.

Bill Clark via Getty Images The Culinary Union headquarters in Las Vegas. The union is a powerhouse in Nevada politics.

To many labor activists, that itself is an argument for Medicare for All. If members had health care through single payer, they could pour all their resources into winning better pay and other benefits. What union wouldn’t love to take a messy and expensive issue like health care off the bargaining table for good? But from the Culinary’s perspective, Medicare for All could scrap a health plan their members like and replace it with something untested, with no refund on the capital they spent in the past to build it up.

Sanders himself has acknowledged the misgivings some unions might have with his health plan, and proposed a wrinkle after taking heat on the trail. The language he added over the summer would allow unions to renegotiate contracts with employers so that any savings from Medicare for All would be pumped into wage and pension increases. His centrist opponents pounced and accused him of backtracking and watering down his plan.

Unions are rarely in lockstep on any complicated issue, and Medicare for All is no different. While the Culinary might oppose single payer, other unions and labor leaders have come out in support of it. Randi Weingarten of the American Federation of Teachers has said she would much rather bargain over class sizes than health care. Sara Nelson of the Association of Flight Attendants has been an outspoken backer of single payer, as has National Nurses United, an ally of Sanders.

Ethan Miller via Getty Images Political door hangers are stacked before a rally with union members at the Culinary Workers Union Hall Local 226 on November 5, 2018 in Las Vegas, Nevada.

“Over the years members sacrificed wage and other economic increases to achieve employer paid health care for them and their families ― now every contract cycle is a fight to maintain it,” said Sal Rosselli, president of the National Union of Healthcare Workers, which has endorsed Sanders and Sen. Elizabeth Warren (D-Mass.). “Medicare for All would take health care off the bargaining table so improvements could be made to pensions, wages, training, child/elder care and other economic issues.”

Even the Culinary membership itself is almost certainly divided on the issue. Sanders faced some tough questions on Medicare for All and some heckling when he spoke before union members in Las Vegas in December. But the Las Vegas Review Journal reported that he otherwise enjoyed an “enthusiastic reception,” with the crowd “firmly behind Sanders” and chanting “Bernie! Bernie!” at times.

The Culinary has not formally endorsed a presidential candidate yet, if it chooses to at all. The union is something of a kingmaker in Nevada politics, with a canvassing and phone-banking operation that can tip elections. It also prides itself on being a ground-up union made up of leaders on the shop floor. How much damage the union’s stance on Medicare for All inflicts on Sanders in Nevada may come down to whether members are really afraid of his plan.

Daniel Marans contributed reporting.