You’d be forgiven for thinking that 2018 is a uniquely worrying moment in America’s great, clamorous experiment with representative government. And you wouldn’t be entirely wrong. Loose talk of a “deep state” seeking to undermine the Trump administration and its allies has entered the political mainstream. Outlandish as the charge might be, we shouldn’t be surprised: Conspiratorial thinking has long had a grip on American politics, and warping effects.

This is the story of one such example, now largely forgotten. It is about an archconservative congressman, Larry McDonald, who became a leader of the New Right, founded his own private intelligence agency and died at the hands of his geopolitical nemesis, all while in office. McDonald was a militant cold warrior and talented zealot who built his own mini-deep state—a foundation that worked with government and law enforcement officials to collect and disseminate information about supposed subversives.

The tale of Representative Larry McDonald might be the weirdest, most unbelievable one in modern American politics that you’ve never heard.

It isn’t entirely without precedent. “Private spy rings can be traced back all the way to the 1920s,” says Darren Mulloy, a professor of history at Wilfrid Laurier University and an expert on radical political and social movements, “or even back to [Allan] Pinkerton’s detective agency at the end of the 19th century.” The tradition picked up during the 1950s, Mulloy says, reportedly with the likes of anticommunist groups like the American Security Council and the John Birch Society.

Such groups “perpetuated conspiracies by gathering so-called intelligence in an effort to discredit people to try and link them to grand and dastardly schemes,” Seth Rosenfeld, author of Subversives: The FBI's War on Student Radicals, and Reagan’s Rise to Power, told me. “So, whether it was a communist conspiracy then, or a ‘deep state’ plot now, these are attempts to undermine people who are dissenting from the powers of the moment.”

It was from this earlier era that McDonald emerged. But in his Cold War story are many lessons for our own age—about the dangers of obsession, and our national obsession over danger.