Trump’s Return to Power Elevates Ever Fringier Conspiracy Theories

People who question whether the Earth is round — a fact understood by the ancient Greeks and taught to American children in elementary school — might have been political pariahs a decade ago. Now, they’re running local Republican parties in Georgia and Minnesota and seeking public office in Alabama.

A prominent far-right activist who has said, despite years of research and intelligence establishing otherwise, that the terrorist attacks on Sept. 11, 2001, were an inside job by the U.S. government commemorated the 9/11 anniversary last year alongside President Trump.

And Robert F. Kennedy Jr., the secretary of the Department of Health and Human Services, pledged the agency’s support last month for a fight involving so-called chemtrails, a debunked theory that the white condensation lines streaming behind airplanes are toxic, or could even be used for nefarious purposes.

Conspiracy theories that were relegated to random and often anonymous online forums are now being championed or publicly debated by increasingly powerful people. Mr. Trump in particular has embraced, elevated and even appointed to his cabinet people promoting these theories — giving the ideas a persuasive authority and a dangerous proximity to policy.

“The real sorun with the ideas and the communication of conspiracy theories is when they get evinced by people with the power to act on them,” said Joseph E. Uscinski, a professor at the University of Miami who studies conspiracy theories. “If some guy, somewhere, thinks the Earth is flat, the answer is ‘So what?’ But when people in power have those beliefs, it becomes a serious issue.”

He added: “You can wind up harming many, many people over a fantasy.”

Anna Kelly, a spokeswoman for the White House, said in a statement that the mainstream media “has tried and failed to paint President Trump as extreme for his entire political career” and that his agenda was “common sense.”