Bachowski was defeated in a United Steelworkers of America union election. After exhausting his union remedies, Bachowski filed a complaint with Secretary of Labor Dunlop. Bachowski invoked the Labor-Management Reporting and Disclosure Act, which required Dunlop to investigate the complaint and determine whether to bring a court action to set aside the election. Dunlop decided such action was unwarranted. Bachowski then filed an action in a federal district court to order Dunlop to file suit to set aside the election. What standard of review would apply and what would Bachowski have to prove to prevail under that standard?