QAnon Cheers Republican Attacks on Jackson. Democrats See a Signal.

That debunked theory held that Satan-worshiping Democrats were trafficking children out of the basement of a Washington restaurant, and in 2017 a believer armed with an assault riffle stormed in and fired his weapon. Judge Jackson, as a district court judge, sentenced him to four years in prison, saying his actions “left psychological wreckage.”

The QAnon conspiracy theory was born a few months later when an anonymous writer — often signing as Q — elaborated on the discredited myth that a cabal of top Democrats was abusing children. Q purported to be a top official close to President Donald J. Trump and asserted that the president was waging a secret war against the cabal.

Slogans about protecting the children became catchphrases that QAnon adherents used to identify one another, and their bizarre fantasy — initially encouraged by far-right news outlets, then promoted by a ring of social media influencers — appeared to spread widely among Trump supporters. At least two Republican lawmakers elected in 2020 had made statements supportive of QAnon, and prosecutors say that many people involved in the Jan. 6, 2021, attack on the Capitol subscribed to the theory.

Among those now echoing the Republican allegations about the judicial nominee, in fact, is Ron Watkins, a former website administrator who is widely believed to have played a major role in writing the anonymous Q posts. Mr. Watkins, who has denied any part in the Q messages, is running for the Republican nomination to an Arizona congressional seat, largely on the strength of his QAnon association; this week, he qualified for the ballot.

“Judge Jackson is a pedophile-enabler,” Mr. Watkins wrote Wednesday on social media. “Any senator who votes to confirm her nomination is also a pedophile-enabler.”

QAnon Telegram channels on Wednesday grew increasingly agitated. “She has committed unbelievable crimes against humanity with her judgeship,” one user wrote. “If she gets confirmed the victims remain victims & trapped in the misery bestowed on them,” said another. Some talked of violence.

Polls suggest that QAnon supporters have continued to make up a significant portion of the Republican base even after Mr. Trump’s departure from office contradicted Q’s predictions. One poll last October found that about 60 percent of Trump voters had heard of QAnon, and 3 out of 10 of those Republicans viewed it favorably.