In times of crisis, American presidents have beckoned us to deny fear, resist our adversaries and come to greatness. Past presidents have asked us to rally, to recognize what unites us, and asserted our cherished values. Today, however, we have entered an age of presidential rhetoric unlike any other. Rather than summoning us to our greatest intentions, President Donald Trump stokes the fires of conspiracy to insist that the danger lies within, in the very institutions that insure the life of our republic.

Donald Trump is America's conspiracy theorist in chief. Unlike other plot finders, his strength is not in the details; he does not reveal the spider-like web of intrigue. Instead, he rapidly spins his theories in tweets and sound bites that are immediately disseminated and command national and global attention. No conspiracy theorist has risen so high. None has had so much influence.

For Trump, the sweep of conspiracy is vast. President Obama is at the heart and was his first target. Trump questioned Obama's American birth and asked whose hidden hands manipulated his rise to the presidency? He warned of a "Manchurian Candidate" elected to the presidency but actually subject to the will of global insiders and power brokers. During the 2016 election, Trump saw "a concerted effort" by the writers of Saturday Night Live, the Daily Show, CNN and the New York Times to defeat his campaign. He claimed that Speaker of the House Paul Ryan, the Democrats and the media had concocted a "sinister deal" to keep him from the presidency.

More nefarious was an international banking conspiracy with branches in Mexico and Europe ready to use its resources against him. Then came charges of a "rigged" election to rebuff the will of the people. The Democrats had welcomed the undocumented not only to America but also to its voting booths.

Along the way, he accused American Muslims of concealing evidence of their co-religionists' terrorist plots, Hillary Clinton's handlers of disguising her incapacitating illness, the National Security Agency of secreting his opponent's emails, the Chinese government of fabricating a climate change hoax, and Senator Ted Cruz's father of involvement in the assassination of John F. Kennedy.

When Trump plays the conspiracy card he follows the standard conspiracist's script, creating a world of good and evil, right and wrong, without nuance.

Victory not only sharpened his world view but also emboldened him. U.S. intelligence and military agencies were part of a dark state undermining his presidency. These hidden Obama agents were even guilty of tapping his telephone during the presidential campaign. They have also penetrated the Labor Department and fabricated "fake" employment statistics to trick American voters. Having failed to stop his election and in league with the media and the Democratic Party, these enemies of the people were eager to strangle the administration at birth and deny the popular will.

Note the conspiracy theorists' methods and goals. In exposing the "facts," they pose as latter-day Paul Reveres determined to save the people from the hidden menace. Preaching that the conspirators are within the gates and the government, they undermine faith in leaders and institutions. Opponents are not simply wrong or misguided. They have betrayed the nation's sacred trust.

For decades, conspiracy theorists worked on the margins of American society. Their claims of global insiders, alien spacecraft, and faked moon landings often-elicited amusement. But, in the last 20 years, the pace of conspiracy thinking has quickened, and the internet has created a worldwide community of linked and determined believers. With a practiced plot weaver at the pinnacle of American power, the fear of conspiracy may come to threaten the very values and rights it pretends to protect.

Robert A. Goldberg is a professor of history and director of the Tanner Humanities Center at the University of Utah.