Georgia’s U.S. Senate race between Republican David Perdue and Democrat Michelle Nunn is flush with spending from nonprofit agencies that keep their donors anonymous, making it one of the most expensive contests of the midterm elections. The emergence of 501(c4) nonprofits and 501(c6) trade groups as prolific spenders on television advertisements that support or oppose particular candidates can be tied to the Supreme Court’s 2010 Citizens United decision, which opened the door to a wave of corporate money influencing political campaigns. For the most part, these groups can spend unlimited amounts of money while not being required to disclose their donors.