Updated on June 17, 2017 at 7:51 p.m. ET

The catastrophe wasn’t what it seemed. It was an inside job, people whispered. Rome didn’t have to burn to the ground.

Nearly 2,000 years ago, after the Great Fire of Rome leveled most of the city, Romans questioned whether the emperor Nero had ordered his guards to start the inferno so he could rebuild Rome the way he wanted. They said the emperor had watched the blaze from the the summit of Palatine Hill, the centermost of the seven hills of Rome, plucking his lyre in celebration as countless people died. There’s no evidence of this maniacal lyre-playing, but historians today still debate whether Nero orchestrated the disaster.

What we do know is this: Conspiracy theories flourish when people feel vulnerable. They thrive on paranoia. It has always been this way.

So it’s understandable that, at this chaotic moment in global politics, conspiracy theories seem to have seeped out from the edges of society and flooded into mainstream political discourse. They’re everywhere.

That’s partly because of the richness of today’s informational environment. In Nero’s day, conspiracy theories were local. Today, they’re global. The web has made it easier than ever for people to watch events unfold in real time. Any person with a web connection can participate in news coverage, follow contradicting reports, sift through blurry photos, and pick out (or publish) bad information. The democratization of internet publishing and the ceaseless news cycle work together to provide a never-ending deluge of raw material that feeds conspiracy theories of all stripes.

From all over the world, likeminded people congregate around the same comforting lies, explanations that validate their ideas. “Things seem a whole lot simpler in the world according to conspiracy theories,” writes Rob Brotherton, in his book, Suspicious Minds: Why We Believe Conspiracy Theories. “The prototypical conspiracy theory is an unanswered question; it assumes nothing is as it seems; it portrays the conspirators as preternaturally competent; and as unusually evil.”

But there’s a difference between people talking about outlandish theories and actually believing them to be true. “Those are two very different things,” says Joseph Uscinski, a political science professor at the University of Miami and the co-author of the book American Conspiracy Theories. “There’s a lot of elite discussion of conspiracy theories, but that doesn’t mean that anyone’s believing them any more than they did in the past. People understand what conspiracy theories are. They can understand these theories as political signals when they don’t in fact believe them.”

And most people don’t, Uscinski says. His data shows that belief in partisan conspiracy theories maxes out at 25 percent—and rarely reach that point. Imagine a quadrant, he says, with Republicans on the right and Democrats on the left. The top half of the quadrant is the people of either party who are more likely to believe in conspiracy theories. The bottom half is the people least likely to believe them. Any partisan conspiracy theory will only resonate with people in one of the two top-half squares—because to be believable, it must affirm the political worldview of a person who is already predisposed to believe in conspiracy theories.

“You aren’t going to believe in theories that denigrate your own side, and you have to have a previous position of buying into conspiracy logic,” Uscinski says.

Since conspiracy theories are often concerned with the most visible concentration of power, the president of the United States is a frequent target. “So when a Republican is president, the accusations are about Republicans, the wealthy, and big business; and when a Democrat is president, the accusations focus on Democrats, communists, and socialists.”

“Right now,” he added, “Things are little different. Because of Donald Trump.”

As it turns out, the most famous conspiracy theorist in the world is the president of the United States. Donald Trump spent years spreading birtherism, a movement founded on the idea that his predecessor was born outside the country and therefore ineligible for the nation’s highest office. (Even when Trump finally admitted in September that he knew Barack Obama was born in the United States, he attempted to spark a new conspiracy.)

Now, Trump’s presidency is the focus of a range of conspiracies and cover-ups—from the very real investigation he’s under to the crackpot ideas about him constantly being floated by some of his detractors on the left. Like the implication that Paul Ryan and Mitch McConnell are involved in a money laundering scheme with the Russians, plus countless more theories about who’s funneling Russian money where and to whom.

“The left has lost its fucking mind, and you can quote me on that,” Uscinski said. “They spent the last eight years chastising Republicans about being a bunch of conspiracy kooks, and they have become exactly what they swore they were not. The hypocrisy is thick and it’s disgusting.”

Trump’s strategy in the face of all this drama has been to treat real and fake information interchangeably and discredit any report that’s unflattering to him. It’s why he refers to reputable news organizations as “fake news,” and why he brags about “going around” journalists by tweeting directly to the people. He wants to shorten the distance between the loony theories on the left and legitimate allegations of wrongdoing against him, making them indistinguishable.

“How does Jones, who traffics in these outrageous conspiracy theories, have the respect of the president of the United States and an audience of millions?”

Pushing conspiracy theories helped win Trump the presidency, and he’s now banking on the idea that they’ll help him as president. He’s casting himself as the victim of a new conspiracy—a “witch hunt” perpetrated by the forces that want to see him fail.

“Donald Trump communicates through conspiracy theories,” Uscinski says. “You can win the presidency on conspiracy theories, but it’s very difficult to govern on them. Because conspiracy theories are for losers, and now he’s a winner.”

What he means is, conspiracy theories are often a way of expressing an imbalance of power by those who perceive themselves to be the underdog. “But if you control the Supreme Court, the Senate, the House, and the White House, you can’t pull that,” Uscinski says. “Just like how Hillary Clinton can’t, in 1998, say her husband’s troubles are due to a vast right-wing conspiracy.”

Donald Trump may be the most famous conspiracy theorist in America, but a close second is the Infowars talk-radio personality Alex Jones, who has made a name for himself spewing reprehensible theories. He claimed the Sandy Hook Elementary School massacre was a hoax. He says 9/11 and the Boston Marathon bombings were carried out by the U.S. government. Jones has an online store where he peddles products like iodine to people prepping for the apocalypse.

Jones has long been a controversial figure, but not enormously well known. That’s changing. Jones was a vocal supporter of Trump, who has in turn praised Jones. “Your reputation is amazing,” Trump told him in an Infowars appearance in 2015. “I will not let you down.” Jones has claimed he is opening a Washington Bureau and considering applying for White House press credentials.

The latest Jones drama is a three-parter (so far): First, the NBC News anchor Megyn Kelly announced she had interviewed Jones, and that NBC would air the segment on Sunday, June 18. Next came the backlash: People disgusted by Jones blasted Kelly and NBC, saying a man whose lies had tortured the families of murdered children should never be given such a prominent platform. Even Jones joined the fracas, saying he’d been treated unfairly in the interview. Finally, on Thursday night, Jones claimed he had secretly recorded the interview, and would release it in full. (So far, he has released what seems to be audio from a phone conversation with Kelly that took place before the interview.)

Kelly has defended her decision to do the interview in the first place by describing Jones’s popularity: “How does Jones, who traffics in these outrageous conspiracy theories, have the respect of the president of the United States and an audience of millions?” The public interest in questioning a person like Jones, she argues, eclipses any worries about normalizing his outlandish views. The questions are arguably more valuable than the answers.

Many journalists agree with Kelly’s reasoning. But it’s also true, scholars say, that giving a platform to conspiracy theorists has measurable harmful effects on society. In 1995, a group of Stanford University psychologists interviewed people either right before or right after they’d viewed Oliver Stone’s 1991 film JFK, which was full of conspiracy theories. Brotherton, who describes the findings in Suspicious Minds, says people leaving the movie described themselves as less likely to vote in an upcoming election and less likely to volunteer or donate to a political campaign, compared with those walking in. “Merely watching the movie eroded, at least temporarily, a little of the viewer’s sense of civic engagement,” Brotherton writes.

There are other examples of real-world consequences of giving platforms to conspiracy theorists, too. The conspiracy theory known as Pizzagate, which rose to prominence across websites like 4chan and niche conservative blogs, resulted in a man firing a weapon in a Washington, D.C., pizza parlor.

The debate over Kelly’s interview comes on the heels of another high-profile conspiracy theory that sent shockwaves through conservative media circles. At the center of that scandal was the TV host Sean Hannity pushing a conspiracy theory about the unsolved murder of a Democratic National Committee staff member and an explosive Fox News report about the murder that was eventually retracted.

* * *

There’s a popular science-fiction podcast, Welcome to Night Vale, developed around the idea of life in a desert town where all conspiracy theories are true. It was first released in June 2012, the summer before a U.S. presidential election, at a moment when Trump was test-driving a new anti-Obama conspiracy. “I wonder when we will be able to see @BarackObama’s college and law school applications and transcripts,” he tweeted the day Night Vale launched. “Why the long wait?”

Joseph Fink, who co-created the podcast, says conspiracy theories today are continuing to function the way they always have. Conspiracy theories are easy ways to tell difficult stories. They provide a storyline that makes a harsh or random world seem ordered. “Especially if it’s ordered against you,” he says. “Since, then, none of it is your fault, which is even more comforting.”

“That said, more extreme conspiracy theories are becoming more mainstream, which is obviously dangerous,” Fink adds. “Conspiracy theories act in a similar way as religious stories: they give you an explanation and structure for why things are the way they are. We are in a Great Awakening of conspiracy theories, and like any massive religious movement, the same power it has to move people also is easily turned into a power to move people against other people.”

Look for the last awakening of this sort in the United States, and you’ll find a sea of similarities—of course, as conspiracy theories tell us, it’s easy to find connections when you go looking for them. Several scholars—people who focus on real conspiracies and people who study conspiracy theories—say the paranoia surrounding the Trump presidency evokes the tumult surrounding the Vietnam War. It’s not that conspiracy theories weren’t, at times, rampant before that. In the 1940s and 1950s, McCarthyism and the trial of Alger Hiss brought with them a surreal spate of hoaxes and misinformation. But it was the assassination of President John F. Kennedy that set off a “general sense of suspicion” that would permeate the culture for some time, says Josiah Thompson, the author of Six Seconds in Dallas: A Micro-Study of the Kennedy Assassination.

“Part of that was, what occurred almost immediately after the assassination, in the years afterward, was Vietnam,” Thompson said, “And over time, a complete loss of confidence in what ever the government was saying about Vietnam. That was not just from the presidency, that was from the government itself.”

This was also a period in which some of the most dramatic ideas that had been disparaged as conspiracy theories turned out to be true. “I am not a crook,” Nixon had insisted. Less than a year later, he resigned. Nixon and Trump are compared not infrequently. Not all presidents are so thin-skinned and antagonistic to the press. Jennifer Senior, reviewing a recent Nixon biography, wrote that “the similarities between Nixon and Trump leap off the page like crickets.” Nixon may have been increasingly paranoid in the final months of his presidency, but he didn't have access to the technology that Trump uses to showcase his conspiracy mindedness.

“With real conspiracy theorists, there’s a kind of—how to put it—almost a dialectic operative,” Thompson says. “Like Trump. You have to keep making wilder and wilder pronouncements over time to hold your audience.”

I tell Thompson the idea Uscinski had shared, about how a person can win the presidency on conspiracy theories, but how they don’t work so well once you’re president. He seems to agree. “In a campaign, what you’re trying to do is affect people’s opinions that will be harvested on one day,” he said. “But governing doesn’t have to do with people’s opinions. It has to do with facts. That’s the real difference.”

When the facts are disputed, of course, you do the best you can with the evidence you can find. Josiah Thompson, the author of Six Seconds in Dallas: A Micro-Study of the Kennedy Assassination, has spent years thinking about all this. When I bring up the enormity of unknown unknowns in people’s understanding of history, Thompson quotes the writer Geoffrey O’Brien: “‘History unfolds as always in the midst of distraction, misunderstanding, and partially obscured sight-lines,’” Thompson says, reading a line from O’Brien’s 2016 review of the novel Black Deutschland by Darryl Pinckney.*

“And that’s the trouble,” Thompson says. “What may appear as conspiracy theory at one point turns out to be truth at another.”

I ask Thompson how sure he is about the official explanation of the JFK assassination, that there was one gunman who fired on the president’s motorcade from the Texas School Book Depository.

Thompson believes, based on controversial acoustic evidence, that on November 22, 1963, a shot was fired from the grassy knoll at Dealey Plaza—not just from the depository. “The acoustics give us a kind of template for how the event occurred—these two flurries of shots, separated by about six seconds.” (Thompson later clarified that he believes the flurries of shots were 4.6 seconds apart.) He says it was two shots in the second flurry that killed Kennedy.**

Thompson pauses.

“Does that make me a conspiracy theorist?”

He laughs.

“After all these years? What do you think?”

* This article originally quoted Josiah Thompson as having said, “history unfolds, as always, in the midst of distraction, misunderstanding, and partially obscured sight-lines.” After publication, Thompson clarified that he had been quoting the New York Review of Books writer Geoffrey O’Brien, who first wrote the line in his review of the Darryl Pinckney novel Black Deutschland.