Bills that would make Michigan the 24th state to adopt a right-to-work law have passed the Michigan Senate and House, both in Republican hands. If the bills are reconciled, as seems likely, the legislation will be signed by the Republican governor.

This is a remarkable event. Michigan is the fifth-most unionized state in the country, with 19.2 percent of the workforce. The United Auto Workers, born in Michigan, has been a major player in state politics for decades.

But the Michigan economy is doing very poorly, relative to the country as a whole, with unemployment at 9.1 percent. Only five states are doing worse. The state’s biggest city, Detroit, is a poster child for urban decay, on the brink of bankruptcy thanks to decades of spectacularly corrupt government and unaffordable pension agreements with its unionized workers.

Right-to-work states have been overwhelmingly concentrated in the South, the mountain West, and the northern plain states. But this year Indiana became the first state in the Midwest industrial heartland to adopt a right-to-work law. Should Michigan do so as well, it will be a powerful indication that union power is in serious and probably permanent decline. No longer obliged to belong to a union in order to work at a unionized company or government, many workers will simply stop paying the substantial dues unions charge. And since, as California’s Jesse Unruh explained decades ago, “money is the mother’s milk of politics,” that means union political power will diminish accordingly.