Political donors have undermined “the very legitimacy of our democracy,” according to Russ Feingold, a former Democratic U.S. Senator from Wisconsin. In a recent op-ed in The British Guardian newspaper, he blames a whole host of villains for this fate: billionaire contributors like Robert Mercer, citizen groups like the National Rifle Association, and so-called “dark money” organizations in general.

To advocates of campaign finance restrictions like Feingold, using money to express political views makes politics more corrupt and extreme. Even though the figures he names are well-known in their political leanings, Feingold claims that their influence in politics is due to the privacy afforded to them by law. The solution, he says, is public disclosure of “dark money.”