Michigan Governor Rick Snyder’s decision to sign a right-to-work law is just the latest battle in Midwestern Republican legislators’ convulsive campaign to eviscerate union political clout. Lansing, Michigan, now follows Madison, Wisconsin, Columbus, Ohio, and Indianapolis, Indiana, as a state capital flooded by union partisans — in a spirited, but vain, effort to forestall these laws.

Unions stand at the core of the Democratic coalition today. They are the last organizations remaining on the liberal side that can effectively appeal to white, working-class men in the Rust Belt swing states. They were crucial to President Barack Obama’s victory there.

So whatever the opposition and the shady legislative tactics, Snyder, his billionaire backers and the rest of the Michigan GOP made the cold political calculation: Break unions’ political power now by stripping them of the ability to raise the funds needed to hire staff, mobilize voters and keep up liberal pressure on state and local officials in the months after the election. Even as Citizens United allows many conservatives to raise unlimited funds, Democratic Party prospects are likely to plummet — turning Michigan as steadily red as Texas....