The U.S. Supreme Court on Monday will consider for the second time in two years whether to choke off a critical funding stream for public-employee unions, potentially reducing organized labor’s influence in the workplace and at the ballot box. The nine justices will hear a challenge backed by anti-union groups to the legality of fees that workers who are not members of unions representing teachers, police, firefighters and certain other government employees must pay to help cover the costs of collective bargaining with state and local governments. About two dozen states require payment of these so-called agency fees, covering roughly 5 million public-sector workers, that provide millions of dollars annually to unions.