But the industrial Midwest resisted.

Those days are gone. After a wave of Republican victories across the region in 2010, Indiana and then Michigan enacted so-called right-to-work laws that supporters said strengthened those states economically, but that labor leaders asserted left behind a trail of weakened unions.

Now it is Wisconsin's turn. On Monday, Gov. Scott Walker — who in 2011 succeeded in slashing collective bargaining rights for most public sector workers — signed a bill that makes his state the 25th to adopt the policy and has given new momentum to the business-led movement, its supporters say.