The flood of falsehoods showed how ingrained misinformation has become inside the G.O.P., where the reflexive response of the rank and file — and even a few prominent figures — to anything that might cast a negative light on the right is to deflect with more fictional claims, creating a vicious cycle that muddies facts, shifts blame and minimizes violence.
It happened after the Jan. 6, 2021, attack on the Capitol, which was inspired by Mr. Trump’s lie of a stolen election, and in turn gave rise to more falsehoods, as Republicans and their right-wing allies tried to play down, deny or invent a different story for what happened, including groundlessly blaming the F.B.I. and antifa. Mr. Pelosi’s attacker is said to have believed some of those tales.
“This is the dynamic as it plays out,” said Brian Hughes, a professor at American University who studies radicalism and extremism. “The conspiracy theory prompts an act of violence; that act of violence needs to be disavowed, and it can only be disavowed by more conspiracy theories, which prompts more violence.”
The Justice Department moved swiftly to bring criminal charges against the suspect in the attack, David DePape, 42, who prosecutors said broke into the Pelosi home intending to kidnap Ms. Pelosi and shatter her kneecaps, and assaulted her husband with a hammer, leaving him with a cracked skull. The San Francisco district attorney said it was imperative for prosecutors to present the facts to the public, given the misinformation circulating widely about the case.
But by then, it was far too late. In a pattern that has become commonplace, a parade of Republicans — helped along by right-wing media personalities including the Fox New host Tucker Carlson, and prominent people including the newly installed Twitter owner Elon Musk, the world’s wealthiest man — had already abetted the viral spread of lies about the attack, distorting the account of what happened before facts could get in the way. Finding life on far-right websites and the so-called dark web, conspiracy theories and falsehoods leaped from the fringes to the mainstream.