It’s no secret that with the 2010 Supreme Court case Citizens United came the undue influence of corporate money on elections. What’s remained mysterious is exactly how partisan advocacy organizations with patriotic-sounding names (like American Tradition Partnership) hide, wash, and funnel money to the candidates of their choice. In her new documentary Dark Money, Kimberly Reed, with the help of journalist John S. Adams and using Montana politics as a case study, deftly explains with interviews and whiteboards how camouflaged private funds influence public policy. She calls for new laws to reveal cash flow sources, and she makes her arguments clearly and convincingly, going out of her way to interview all sides. Reed says, rightly, that the issue isn’t a Democratic or Republican problem, but a general constitutional crisis. Be sure to see it but bring a cool drink. It’ll make your blood boil.