Three years later, union leaders say the bill they fought to pass now threatens to hurt their own members. At issue are the collectively bargained, multi-employer insurance plans that more than 15 million unionized workers access under the Taft-Hartley Act. Those plans currently allow workers like builders and electricians to change jobs among participating employers and stay in the same health-insurance plan. Because many of the jobs involve manual labor, the plans usually account for injuries and repetitive stresses, benefits that unions say their workers sought instead of higher wages.

But this could change. Under the Affordable Care Act, small companies could choose to stop covering workers through the union agreements and send their workers to the state-based exchanges instead. Through these exchanges, workers would pay lower premiums, thanks to federal government subsidies. But labor leaders fear that the workers who retain union plans will end up paying higher premiums, since there will be fewer people in the plans, and coverage could be less generous. No one knows for sure that this is how it will play out—companies could very well decide to continue in the union plans and keep the status quo—but unions are predicting the worst.

Republicans are saying “I told you so.” Democrats are saying that while they never meant to hurt their allies in organized labor, their hands are now tied by the House GOP.