Labor supporters say a coordinated campaign by the political right is pushing right-to-work laws with the goal of crippling unions financially so that they can no longer afford to put money into electoral politics and challenge the agenda of billionaires.

“That’s their end game,” said Mark Brenner, a labor economist and the director of the labor education organization Labor Notes. “The conservative wing of the Republican party sees the possibility for eradicating from the map unions as we’ve known them for the last almost 85 years.”

Right-to-work laws used to be confined to conservative, less-unionized states in Plains states, the West and the South.

But lately some traditionally union-friendly states in the industrialized Midwest are also adopting these rules that allow workers to withhold dues or fees from the unions that represent them in bargaining.

Indiana and Michigan have recently jumped on the right-to-work bandwagon, and just last month Wisconsin became the 25th state to pass a right-to-work law.

The statutes can create a vicious downward spiral for unions. As some workers stop paying dues or fees, the union can no longer afford to offer as many benefits and services, which can lead more workers to opt out of paying.

Although right-to-work laws generally cover both the private and public sector, they are sometimes preceded in a state by rules targeting only public employees, such as teachers.

Wisconsin Gov. Scott Walker, for example, initially took aim at the public sector, signing a law in 2011 that stripped public-employee unions of collective-bargaining rights, which went far beyond allowing workers to withhold dues or fees.

The result has been disaster for the state’s unions as an increasing number of workers opt out of union membership. Wisconsin’s teachers union has seen the number of its members drop by a third. The state employees union has seen its membership plunge by 70 percent.

Then this year, Walker went further with a law extending right-to-work to the private sector.

Brenner said conservatives go after public-sector unions first for a few reasons. These unions comprise the bulk of the labor movement. They are far more heavily engaged in electoral politics than private-sector unions, an activity that the right wing would like to end. And public-employee unions tend to have diverse memberships with better benefits than many private-sector workers, making them a prime target for accusations that they are living large at taxpayers’ expense.

“If you’re attacking workers at the Division of Motor Vehicles or post office, what’s the mental picture of a postal worker for a lot of people in this country?” Brenner said. “It’s an African American or Latino or Asian person sitting across the counter from you.”

Those who attack public-employee benefits are “saying in a fairly unsubtle way that ‘those people’ don’t deserve what they have,” Brenner said.

Some observers believe New York State could become a battleground for right-to-work legislation. The bigger threat, however, comes from Washington, D.C., said Ed Ott, the former executive director of the New York City Central Labor Council.

If conservatives “can get a majority of states to have right-to-work laws,” Ott said, “they’ll be screaming, ‘Most people don’t want these protections. We need a national right-to-work law.’”