“American politics has often been an arena for angry minds,” the political scientist Richard Hofstadter wrote 60 years ago in his classic essay, “The Paranoid Style in American Politics.” Yet across many eras, this discourse of  “heated exaggeration, suspicion and conspiratorial fantasy” festered largely on the fringe. Then the internet made the fringe accessible to everyone, amplifying dissonance and disinformation.

In the initial hours after the shocking assassination attempt against Donald Trump on Saturday evening, meme-makers and influencers on the left and right came to fast agreement about one thing: the shooting must have been orchestrated. Some on the left described it as a false-flag operation staged to make Mr Trump look invincible and bolster his election prospects. They pointed to the way Mr Trump paused to pose for photos with his fist in the air and blood streaking down his cheek as evidence that the attack must have been choreographed by the candidate’s own image-makers.