The threatened benefit cuts, which could impact 1.5 million retirees and workers, stem from deep financial problems affecting some multiemployer pension plans – traditional defined benefit plans jointly funded by groups of employers – typically in industries like construction, trucking, mining and food retailing.

More than 10 million U.S. workers and retirees are covered by 1,400 of these plans – many of them in Trump-supporting U.S. Rust Belt states like Ohio and Michigan.