The documentary Dark Money, now airing free on PBS after it received very positive reviews at Sundance this spring, focuses primarily on a very specific case of electoral manipulation in Montana, where the Koch brothers used various 501(c)(4) front groups – “social welfare” nonprofits that don’t have to disclose their donors – to flood districts with misleading or fraudulent materials in the last 30 days before elections. Montana’s history of restrictive campaign finance laws and tradition of citizen legislators makes it the ideal environment to expose these methods, which are at least subversive and unethical even when they’re not illegal, but a system designed to thwart such manipulation still wasn’t enough to stop it or make it easier to detect or fight. And, as the filmmakers show throughout the story, what happened in Montana is increasingly happening elsewhere, with the Koch brothers in particular behind much of it in their fights to eliminate labor unions, demonize public education, and gut environmental regulations on businesses. It’s horrifying, and Dark Money makes it clear that we the people have few if any tools available to stop it.

Dark Money largely follows the work of an investigative reporter named John S. Adams, who was let go when the state’s largest newspaper group shuttered its office covering state affairs and decided to start working on this case on his own. In several elections for the state legislature, candidates found themselves targeted by mailers that included inflammatory and often false claims, but were unable to effectively respond to them because they arrived at voters’ houses so late – and because responding would have required campaign funds they didn’t have. These mailers came from ‘dark money’ groups, nonprofits with innocuous names who don’t have to disclose their funders’ identities and in many cases don’t exist beyond a PO Box. Adams, with the help of some of the targeted candidates (many of whom were Republicans who were primaried from the right by candidates aided by dark money groups) and eventually some volunteer attorneys who helped the state build its case against one legislator, did his best to follow the money, and with some good fortune was eventually able to show that the Koch group Americans for Prosperity was behind the mailers. The film follows one specific case, against Republican Art Wittich, for accepting illegal contributions from the National Right to Work Committee, which is largely funded by the Koch brothers. The group has even continued meddling in Montana elections past the court case and timeline covered in the documentary.

Filmmaker Kim Reed does a superb job generalizing the case to constituencies beyond Montana, including showing how the Koch brothers and affiliated groups helped rig the recall election of Scott Walker and stack the Wisconsin Supreme Court with allies who shut down a state investigation into the Walker campaign’s finances. The IRS regulation on 501(c)(4) groups, which are categorized as “social welfare” organizations, is one major obstacle to allowing voters to know who’s funding those mailers or donating to political candidates. Another is the emasculation of the Federal Election Commission that began under Don McGahn, who joined the FEC with two other Republicans and made a pact to always vote in a bloc that effectively prevented the Commission from doing anything, killing the group’s authority to adjudicate in cases of campaign finance violations. (The FEC, by design, is a six-member panel, with three commissioners from each party, and thus is prone to 3-3 ties along party lines.)

And the third, of course, is the 2010 Supreme Court ruling Citizens United v. FEC, where the Court ruled 5-4 that corporate donations to political campaigns were protected speech under the First Amendment – thus arguing that corporations, which are legal entities, have the same free speech rights as people. (Corporations primarily exist in law as a way to shield investors or owners from many forms of legal liability; they also enjoy different tax benefits from individuals, and also allow owners to gain from economies of scale not available to smaller entities. Corporations may act as individuals in the economic sphere, but they are not individual actors in the political space, or at least were not until Citizens United.) The rise of dark money also has created the possibility or even likelihood that foreign corporations or governments are funding American political campaigns; who’s to say that Chinese companies or the Russian or North Korean governments aren’t funding American Tradition Partnership or other front groups that support mostly conservative candidates who have agreed to reduce or eliminate regulations in exchange for campaign support?

There is so much to infuriate voters in Dark Money; even if you agree with these astroturfing groups’ policy aims, do you really agree with their methods? Should campaign funding be untraceable? Should there be consequences for sending out fliers with misleading or false statements against candidates? To what extent should corporate money be involved in politics when, as described in the documentary, those candidates will in turn vote on matters like environmental regulations where the interests of the companies funding candidates do not align with those of voters (assuming voters like clean water)? One of the many examples in the film that serves as a microcosm for the increasingly dirty, toxic atmosphere of our body politic is when the Montana branch of Americans for Prosperity holds a “town hall” meeting, promising voters they can ask a specific candidate why he’s supporting Obamacare or voting certain ways on issues … but didn’t invite the candidate himself, despite using his name and image on fliers advertising the event. The candidate shows up, and the group’s director, Zach Lahn (now involved in a Koch-funded primary school in Wichita, despite having no background in education) claims he left the candidate “two messages,” and then tells a voter that he didn’t lie about the event because he used a “different definition of town hall.” Our rights are at stake, and we don’t know who’s paying for the information that shows up in our mailboxes, or to whom the names on the ballot might be beholden once they’re elected. Even if you don’t care about the methods used to get the candidates you think you want in office elected, once they’re there, they may be voting for a lot of things you didn’t know they’d support. Dark Money is the ultimate cautionary tale as our republic’s foundations begin to crack.