The clash between Republicans and Democrat-backed labor unions is spreading from Wisconsin to Indiana and Ohio. Last week, teachers, students, and prison guards protested a Wisconsin bill to limit public-sector unions’ collective-bargaining powers, while Democratic lawmakers fled the state to prevent a vote on the legislation. Thousands of steelworkers, autoworkers, and other labor activists protested outside the Indiana state capitol on Monday, rallying against a potential bill that would weaken the power of private-sector unions, while Indiana Democrats contemplated a walkout to stall the bill, claiming the GOP is assaulting the middle class. In Ohio, where Republicans are trying to restrict collective-bargaining rights for 400,000 public employees, union officials are anticipating 5,000 or more protesters on Tuesday. Labor unions expect the protests to spill over into a dozen other states as well.