If you are already dismayed at the spending and tactics that have characterized this election season, better stay away from Tuesday’s episode of “Frontline” on PBS. The piece, “Big Sky, Big Money,” looks at the shenanigans in Montana in the last four years, and the picture it paints of American electioneering certainly suggests a beast out of control.

Kai Ryssdal is a patient and clear guide through the Supreme Court decision on Citizens United, the rise of “super PACs” and the rules governing 501(c)(4) advocacy groups. He shows how these forces have shaped recent votes in Montana, including the current battle for a pivotal United States Senate seat between Jon Tester, the incumbent Democrat, and Denny Rehberg, a Republican member of the House of Representatives.

Mr. Ryssdal manages to get himself a tour of American Bridge 21st Century, a Democratic-leaning super PAC, and he interviews James Bopp Jr., the lawyer who initiated the Citizens United case and who continues to push for the dismantling of campaign-financing restrictions. “The average voter could care less who’s funding a politician,” Mr. Bopp asserts.

Mr. Ryssdal’s main interest, though, is in examining the activities in Montana of 501(c)(4) groups, which are not required to disclose their donors but are supposed to stick to issues rather than advocate for, or work with, candidates (a restriction some try to circumvent with carefully worded messages). Finding out who is behind such groups, he notes, is next to impossible.