Republicans crushed a weaker opponent in Michigan this week, passing a right- to-work law that infuriated unions. But the effort -- an attempt to defund and depopulate Democratic campaigns by defunding and depopulating unions – points to some of the difficulties Republicans face due to a diminished coalition.

The law exempted Republican-friendly police officers and fire fighters, thereby underscoring the naked politics behind it. But more than 17 percent of Michigan workers are members of a union, one of the highest rates of unionization in the nation.

Crushing unions benefits Republicans. Given that white working-class men are one of the last loyal Republican constituencies, however, the victory is not necessarily cost-free. According to exit polls, 14 percent of voters in the Michigan Republican primary in February were union members. It’s doubtful Republicans gained any new supporters with their action this week; it’s possible they lost a few.

Back in Washington, House Speaker John Boehner is trying to avoid offending an even more crucial constituency: the elderly. Mitt Romney lost big among young people in November but he beat Barack Obama among voters between the ages of 45 and 64 by 51 to 47. Among voters 65 and older, it was Romney who won big, 56 to 44.

Boehner wants to wring concessions from Obama largely in the form of cuts to Medicare, Medicaid and Social Security. Most of the beneficiaries of those programs have something in common beyond their good looks, which is why Boehner is desperate to avoid Republican fingerprints on the cuts.

Once Republicans get through cutting benefits to the elderly, perhaps they’ll look for concessions from Nascar fans living below the Mason-Dixon line.

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

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