The attack on Donald Trump triggered a flood of partisan misinformation

“AAmerican politics “was often a scene of angry tempers,” wrote political scientist Richard Hofstadter 60 years ago in his classic essay “The Paranoid Style in American Politics.” But for many eras, this discourse of “heated exaggeration, suspicion, and conspiracy fantasy” festered largely on the fringes. Then the Internet made the fringes accessible to everyone, amplifying dissonance and disinformation.

In the first hours after the shocking assassination of Donald Trump on Saturday night, meme-makers and influencers on the left and right were quick to agree on one thing: The shooting must have been staged. Some on the left called it a false flag operation staged to make Mr. Trump appear invincible and boost his electoral chances. They pointed out that the way Mr. Trump paused to pose for photos, his fist in the air and blood running down his cheek, was proof that the attack must have been staged by the candidate’s image-makers themselves.