What Tuesday’s rally in Tampa made apparent is that devotees of these falsehoods — some of which are specific to faith in the president, others garden-variety nonsense with racist and anti-Semitic undertones — don’t just exist in the far reaches of the Web.

Believers in “QAnon,” as the conspiracy theory is known, were front and center at the Florida State Fairgrounds Expo Hall, where Trump came to stump for Republican candidates. As the president spoke, a sign rose from the audience. “We are Q,” it read. Another poster displayed text arranged in a “Q” pattern: “Where we go one we go all.”

The symbol appeared on clothing, too. A man and a woman wore matching white T-shirts with the YouTube logo encircled in a blue “Q.” The video-sharing website came under criticism this week for unwittingly becoming a platform for baseless claims, first promoted on Twitter and Reddit by QAnon believers, that certain Hollywood celebrities are pedophiles. A search for the name of one of those celebrities on Monday returned videos purporting to show his victims sharing their stories.

Audience members at a Trump rally on July 31 in Tampa wear T-shirts referring to the “QAnon” conspiracy theory. (The Washington Post)
The prominence of the “Q” symbol turned parts of the audience into a tableau of delusion and paranoia — and offered evidence that QAnon, an outgrowth of the #Pizzagate conspiracy theory that led a gunman to open fire in a D.C. restaurant last year, has leaped from Internet message boards to the president’s “Make America Great Again” tour through America.

“Pray Trump mentions Q!” one user wrote on 8chan. He didn’t need to. As hazy corners of the Internet buzzed about the president’s speech, his appearance became a real-life show of force for the community that has mostly operated behind the veil of anonymity on subreddits.

Trump himself has at times been a purveyor of conspiracy theories, most notably in refusing for years to back down from his false claim that Barack Obama was not born in the United States. He also asserted without evidence that Obama had wiretapped Trump Tower, peddled the debunked idea that millions of illegal votes cost him the popular vote and associated the father of Republican Sen. Ted Cruz of Texas with the assassin who shot John F. Kennedy.

But viewing their message boards, it’s clear that QAnon crosses a new frontier. In the black hole of conspiracy in which “Q” has plunged its followers, Trump only feigned collusion to create a pretense for the hiring of special counsel Robert S. Mueller III, who is actually working as a “white hat,” or hero, to expose the Democrats. Barack Obama, Hillary Clinton and George Soros are planning a coup — and traffic children in their spare time. J.P. Morgan, the American financier, sank the Titanic.

In the world in which QAnon believers live, Trump’s detractors, such as Republican Sen. John McCain of Arizona and Hillary Clinton aide Huma Abedin, wear ankle monitors that track their whereabouts. Press reports are dismissed as “Operation Mockingbird,” the name given to the alleged midcentury infiltration of the American media by the CIA. The Illuminati looms large in QAnon, as do the Rothschilds, a wealthy Jewish family vilified by the conspiracy theorists as the leaders of a satanic cult. Among the world leaders wise to satanic influences, the theory holds, is Russian President Vladimir Putin.

QAnon flirts with eschatology, fascist philosophy and the filmmaking of Francis Ford Coppola. Adherents believe a “Great Awakening” will precede the final storm foretold by Trump. Once they make sense of the information drip-fed to them by “Q,” they will usher in a Christian revival presaging total victory.

The implication is that resolving the clues left by “Q” would not just explain Trump’s planned countercoup. It would also explain the whole universe.

When “Q” is absent for long stretches of time, followers take note.

“Please tell me where to go,” one wrote last month. “I feel lost without Q.”