This week, two of the lesser-known Democrats in the presidential race, Rep. Tim Ryan (OH) and former Rep. John Delaney (MD), suggested on the Democratic debate stage that Sen. Bernie Sanders’s Medicare-for-all plan goes against union interests.

“This plan being offered ... will tell the union members that give away wages in order to get good health care that they will lose their health care because Washington is going to come in and tell them they have a better plan,” Ryan said. Delaney talked about his father, a unionized electrician, suggesting he would “never want someone to take [his health care] away.”

But some of the biggest unions in the country couldn’t disagree more.

“Tim Ryan, that’s a great failure of understanding how unions work,” said Sara Nelson, president of the Association of Flight Attendants. His suggestion was “offensive to me,” she added.

American Federation of Teachers president Randi Weingarten noted that that AFT is supportive of Medicare-for-all and other universal health care plans. “Any plan that provides more people with the care they need and gets us one step closer to affordable coverage is a step in the right direction,” she said.

Both Ryan and Delaney oppose Medicare-for-all on the grounds it is radical, politically unfeasible, and too disruptive to the current health care system. They advocate instead for proposals that would expand coverage while keeping private employer-sponsored plans.

Ryan’s campaign did not respond to multiple requests for comment about where he got this idea. But those close to the labor movement suggested it may come from a vestige of a shrinking and transforming labor movement.

“Ryan, coming from Ohio, really frames this in terms of the union members with hard hats,” said Andrew Feldman, a Democratic strategist who has close ties to the labor movement. “It’s this old guard of labor. What we have seen in the last couple years, is this labor movement that’s made this grassroots resurgence, [like the teachers and service workers]. Those unions have publicly come out and said they would support Medicare-for-all.”

The debate around Medicare-for-all and unions, explained

Delaney and Ryan were trying to pit some Sanders’s biggest priorities — universal health care and worker’s rights — against each other. Their argument centered around the fact that Sanders’s Medicare-for-all bill does away with employer-sponsored insurance and puts every American on an expanded public health care system. They say that unions have fought hard to secure generous health care packages from employers, and shouldn’t have to switch from that.

This debate erupted during the first night of the Democratic debates, as Sanders and Sen. Elizabeth Warren (D-MA), who also supports single-payer, clarified nobody’s insurance would be taken away. And it’s true — Sanders’s proposed plan is more generous than the typical private-sector plan, offering no co-pays or deductibles and covering virtually everything. If it were to pass as proposed, many unions likely would see Medicare-for-all as a better deal.

But even so, Ryan was hellbent on making the case that Medicare-for-all would undo union work.

Here’s the full exchange, which led to Sanders’s most viral moment (when he swore at Ryan):

Sanders: Medicare For All is comprehensive and covers all health care needs. For senior citizens, it will finally include dental care, hearing AIDS and eyeglasses. Second of all — Ryan: You don’t know that, Bernie. Sanders: I do know that. I wrote the damn bill. Second of all, many of our union brothers and sisters, nobody more pro-union than me up here are now paying high deductibles and co-payments and when we do medicare for all, instead of having the company putting money into health care, they can get decent wage increases which they are not getting today. Ryan: Sen. Sanders does not know the union contracts in the United States. I’m trying to explain that these union members are losing their jobs. Their wages have been stagnant. The world is crumbling around them. The only thing they have is possibly really good health care, and the Democratic message is going to be we’re going to go in and the only thing you have left, we’re going to take and do better. I do not think that’s a recipe for success for us. It’s bad policy, and it’s certainly bad politics.

It should be noted that as a member of the House, Ryan has signed on to a Medicare-for-all bill, which would eliminate private insurance. His campaign told the Washington Post’s Jeff Stein that Ryan disagreed with some of the key components of that bill, but signed on hoping it would change in negotiations.

In making this case that Medicare-for-all was bad for unions, Ryan seemed to be echoing why many unions are open to the proposal.

“This is a priority we set in the 1940s, and labor was quite successful in negotiating contractual health care, but every time we go to the table the for-profit system has put so much pressure that when we get what we already have we call that a win,” Nelson told Vox about the difficulties negotiating health care poses. She added that having a government-sponsored baseline health insurance would go a long way to help unions negotiate better wages, and benefits in other areas of their contract.

While there is a wealth of research that has found increased health care costs bring down wage growth, there’s less evidence that companies engage in the trade-off the other way. As Sarah Kliff reported, “there are no studies that show the reverse relationship — wages rising when premiums grow slower — but experts in labor economics believe this relationship exists.”

The labor movement looks very different today than what Delaney and Ryan seem to be talking about

Polling across the board shows that Americans aren’t too fond of the idea of cutting out private health insurance. A Kaiser Family Foundation poll found 56 percent of the public favors “a national health plan, sometimes called Medicare-for-all, where all Americans would get their insurance from a single government plan.” But when told directly that Medicare-for-all would end private insurance, larger margins support more incremental steps toward a government-run program, like lowering the eligibility age for Medicare.

And it’s true that Democrats have some work to do shoring up union members. Clinton underperformed Barack Obama among union workers; white male union members significantly shifted toward Donald Trump, outpacing Clinton altogether to help deliver Trump the presidency.

Those seem to be the voters Ryan is talking about; an older coalition of white working-class voters that defected to Trump.

“I think [Ryan’s argument] may resonate because they are just more conservative in general and many actually voted for Trump,” Feldman said. “I don’t think it’s because they love their private health care.”

But candidates like Warren and Sanders are taking a different approach to the union vote. They recognize that the labor movement as a whole has been attempting to broaden its constituency to a progressive working class that didn’t necessarily see a champion in either Trump or Clinton in 2016. This more diverse working-class group — which includes women, Latinos, and African Americans — represents the fastest-growing share of union membership. And this growing sector of the labor movement might be ready for something different.

“No elected official should accept incrementalism,” Mary Kay Henry, president of Service Employees International Union, one of the largest and most influential unions in North America, told Vox’s Alexia Fernandez Campbell. “American taxpayers are subsidizing multimillion-dollar companies that are making record profits but are not providing decent jobs for people. You can’t nibble around the edges. All these bold solutions are not radical.”

And, Nelson points out, not all union contracts are made the same.

“It is real that there is work to do with unions,” Nelson said. “People do love their contractural plans. But not every union contract today has exemplary health care.”