With a final vote in the legislature scheduled today, Michigan appears set to become the nation's 24th right-to-work state. It would make dues-paying voluntary for private-sector unions and for most public-sector unions other than police and firefighters.

President Barack Obama said yesterday that the law would give residents "the right to work for less money." Union supporters have promised a protest at the state Capitol. But Republican Governor Rick Snyder has said he intends to sign the law, which is all but certain to pass the Republican-controlled legislature.

Republicans cast the measure as a pro-business initiative, and it is supported by the U.S. Chamber of Commerce, among other business interests. But declining union membership, high unemployment and record corporate profits suggest that unions are not exactly a major drag on American business at the moment.

The move follows an ill-conceived referendum, promoted and financed by unions themselves, to enshrine collective bargaining rights in the Michigan constitution. The effort failed at the ballot box in November. That humbling confirmation of union weakness appears to have been the precipitating event for the right-to-work legislation. Republicans, ever mindful of the millions that unions contribute to Democrats each campaign season, would like to gut union membership and drain union coffers. With groups such as the Chamber of Commerce, which is as much an arm of the Republican Party as the United Auto Workers is of the Democratic Party, it's likely they view the conflict as Republican vs. Democrat more than Management vs. Labor.

Union leaders have vowed to continue the cycle of retaliation and recrimination if Snyder signs the right-to-work law. They have even raised the specter of recalling Republican lawmakers, a tactic employed earlier this year in Wisconsin that succeeded largely in adding to the state's oversupply of bitterness, wasted effort and ill will.

It's hard to see what good will come of any of it. Unions, which once covered about one-third of U.S. workers, have been reeling from the decline of U.S. manufacturing and their own failures to adapt. They have made large concessions to Michigan automakers, bringing cost structures in line with nonunion plants in the South. Once virtually guaranteed middle-class prosperity, many auto factory workers now "make less than the $19.10 hourly average U.S. manufacturing wage and lack traditional union retiree benefits," Bloomberg News reported in October. In other words, without unions, working class wages decline. With unions ... wages decline.

In 2011, 11.8 percent -- 14.8 million Americans -- were union members. Among full-time wage and salary workers, union members had median usual weekly earnings of $938 in 2011 compared with $729 for nonunion members. But the factors influencing that difference are many.

It's possible that unions are a relic of an industrial economy that no longer exists. It's also possible that the wages of U.S. workers won't rise -- or even stop eroding -- until unions rebound and prod profitable companies to share more of their proceeds with employees. Unions, workers, employers and politicians will all have a say in which of those paths, or others, points to the future. The particular interest of Republican state legislators in winning more elections shouldn't be a deciding factor in the equation.

Snyder didn't ask for the right-to-work legislation and seemed eager to avoid the confrontation. He had previously vetoed voter ID bills in his state with similarly partisan aims. It took courage, and a strong sense of fair play, for a Republican governor to do that. Perhaps it's too much to expect a politician to be a hero twice.

(Francis Wilkinson is a member of the Bloomberg View editorial board. Follow him on Twitter.)

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