The Supreme Court last year handed down a decision in Janus v. AFSCME that limits the freedom of millions of public sector workers to come together in strong unions and, as a result, threatens all Americans since unions help build the middle class. Janus supporters have now revealed the next step in their strategy to divide workers and erode their power to improve work conditions through members only unions.

The Janus decision creates a perverse incentive for public sector workers not to join a union, as workers covered by a union contract can receive all the benefits of membership without paying the cost of negotiating those benefits. Yet, conservatives are pushing even further to bar unions from representing all employees in a given workplace. In areas with strong public sector unions, this could come at a huge cost. Employers bargain with a union, designated as the exclusive representative for workers, only after a majority of workers said that they want the union. Through their unified voice, workers gain the power to improve conditions.

{mosads}Members only unions would dilute this power by dividing workers and allowing employers to pit them against each other. Today, unions represent a third of all public sector workers. This was not always the case. Excluded from federal labor law, only a small portion of public service workers formed unions until the second half of the last century. They lobbied for government reforms and informally negotiated with employers. But this was no match for the power of private sector unions that increasingly represented workers across entire industries.

In 1960, the average wage of a manufacturing worker was 20 percent higher than that of a public sector employee. This gap motivated public service workers to join unions and demand states and cities around the country recognize their rights. Between 1960 and 1976, unionization rates among state and local employees grew from 5 percent to nearly 40 percent. As unions grew, benefits spread throughout communities. Indeed, high unionization rates raise the pay of all workers, increase the likelihood that poor children will have higher earnings as adults, and allow unions to negotiate in support of broader community needs.

Moreover, winning exclusive representation helped protect women and workers of color from discrimination prior to the passage of federal protections since these provisions ensure unions can defend all workers on the job. For LGBTQ workers in the 29 states that lack full protections against discrimination based on sexual orientation or gender identity, collective bargaining agreements are often their best safeguard. Public service unions have also helped reduce pay gaps for women and workers of color by fighting for practices that ensure that salaries are tied to the jobs they perform, rather than their personal characteristics.

Finally, the elimination of the right to represent all workers could also harm public employers since a single democratically chosen voice for workers provides stability and a mechanism to resolve conflict. As 21 state attorneys general recently wrote, the services of a union serving as the exclusive representative of all of the employees “may be critically important to ensure the delivery of core government services.”

The Janus ruling and push for members only unions are the latest attacks in a decades long war on workers that has eroded unionization rates. Janus supporters have also championed private sector right to work laws, fought to preempt local minimum wage increases, and prevented nearly all public sector bargaining Iowa and Wisconsin, a strategy that Republican Governor Scott Walker referred to as “divide and conquer.”

Despite these attacks, Americans will not give up on the power of unions to speak for all working families. Teachers are joining together to demand better pay and better schools, Missouri voters handily defeated a right to work initiative, and nearly half of Americans say that they would join a union if given the opportunity. Unions are the strongest when they speak for all workers. In communities where public sector unions are strong, members only unions are a step in the wrong direction.

Karla Walter is director of labor policy at the Center for American Progress.