(Bloomberg) — After years of avoiding confrontation, the U.S. labor movement is reasserting itself. From the ports of Los Angeles to the car plants of Detroit, unions are demanding payback for sacrifices they say helped revive the economy.

Oil workers have walked off the job for higher wages and better working conditions. Dock workers have snarled West Coast ports. Personnel staffing oil terminals at the Port of Long Beach, California, are threatening to strike. In Detroit, union leaders girding for contract talks this year will push for the first raise veteran autoworkers have received in a decade.

Union leaders are taking advantage of a tightening labor market and favorable political environment. With middle-class wages stagnating and the rich getting richer, income inequality has become a rallying cry for Democrats and Republicans alike. Reviving opportunity for all resonates with Americans who feel left out as growth picks up and the market notches record highs.