Lee Harvey Oswald, a fame-seeking Communist from New Orleans, acted alone when he assassinated President John F. Kennedy with an Italian-made 6.5-mm Carcano Model 91/38 rifle fired from the Texas School Book Depository window in Dallas 50 years ago on Nov. 22, 1963.

Or did he?

The question of whether Oswald acted alone has produced reams of books that get longer and more convoluted by the year, bent on proving that the Warren Commission was incorrect in its assessment of Oswald as the lone conspirator. Whether it was the bizarre counter-assassination by Jack Ruby or Frame 313 in the Abraham Zapruder film footage of the actual assassination, evidence suggests that Oswald was part of perhaps the greatest American political conspiracy, these authors say.

The Kennedy assassination, however, has no small amount of competition when it comes to American conspiracy theories. In the 18th century, Roman Catholics were rumored to be setting up a shadow government west of the Alleghenies to destroy US liberties. Slave conspiracy paranoia "was one of the most significant cultural phenomena of pre-Civil War America," according to "Conspiracy Theories in American History: An Encyclopedia." And, of course, Sen. Joseph McCarthy was convinced that Communists were corrupting the nation in the 1950s.

While the United States is by no means alone in hatching conspiracy theories, its history gives them a peculiar fervor. In a country where the Founding Fathers' distrust of government is enshrined in the Constitution, conspiracy theories often give wider scope to that worldview.

Now, with the Internet providing a platform for dubious opinions, the fear of drones in American skies, and the belief that the president is actually a foreign-born Muslim, today is a "golden age" for conspiracies, some say.

Such discussions often come with a wink, but the strident tone and sheer ubiquity of conspiracy talk are raising questions about whether the current dysfunction of American democracy is, at least in part, a product of our increasing inability to separate truth from fantasy.

"Distrust of the government's conclusions seems hard-wired," suggests Kenn Thomas, editor of Steamshovel Press, a so-called parapolitical conspiracy magazine, in an e-mail.

Today, 59 percent of Americans scoff at the idea that Oswald acted alone, according to an October poll by The Associated Press. Among Republicans, 62 percent believe that the Obama administration is plotting to subvert the Constitution by disarming gun owners. A more modest 13 percent of Americans believe the US government is involved in "false flag" operations in which shadowy agents plot mass shootings or plant evidence to justify drone killings.

Such theories can find fertile ground in Americans' skepticism toward their own government, which has only grown over the past 50 years. During the presidency of Lyndon B. Johnson, trust in government was at nearly 80 percent; in 2013 it has hit a historic low of 19 percent, according to the Pew Research Center.

President Obama has struggled against claims that he is a Muslim and that his Hawaii birth certificate is a fake. The Clinton years were rife with theories that the administration was using black helicopters to harass opponents and spread its authority, and talk show host Rush Limbaugh gave voice to the rumor that White House aide Vince Foster did not commit suicide but was murdered because of something he knew.

Years later, "9/11 truthers" linked George W. Bush with covert schemes by the global industrial complex to profit from years of war, suggesting C-4 explosives were used to make sure the twin towers came down.

"Conspiracy theories are a particular expression of the populist distrust of power," says Mark Fenster, a University of Florida law professor and the author of "Conspiracy Theories: Secrecy and Power in American Culture." "They are a particularly intense way of telling a populist story and cranking it up to 11 by saying that it's in fact not just the state but ... this small cabal secretly manipulating things."

In that way, conspiracy theories also fill another role: They help shape complex events into a simpler narrative. Even if that narrative is disturbing, the ability to grasp it helps combat feelings of impotence and confusion.

'Conspiracy gives us comfort'

"Sometimes conspiracy gives us comfort," says Sean Cunningham, a history professor at Texas Tech University who has studied the paranoid style of politics. "Even if it creates paranoia and panic – it's something you can hold onto as an explanation of why something happened.

"As people continue to hear for decades after the Kennedy assassination that there are alternative [theories], then it's a Pandora's box as to what else could 'they' have possibly done, and it feeds the fire for any other conspiracy that you can imagine," he adds.

This tendency has been apparent for decades. About the same percentage of Americans who suspected conspiracy behind the 9/11 attacks suspected conspiracy behind Kennedy's death.

The result is that American conspiracy theories have often been a window into their eras.

For example, the fractious years that followed Kennedy's death became folded into the assassination mythology. The assassinations of civil rights leader Martin Luther King Jr. and the president's brother, Robert Kennedy; the Vietnam War; and Watergate together offered an impression of a sinister pattern. The Church Committee, which in 1975 told Congress of the Central Intelligence Agency's myriad abuses of law and power, helped provide the grist for a conspiracy narrative.

At the end of the cold war in the early 1990s, the tone of conspiracy shifted to embrace a new ambiguity. Americans felt suddenly untethered from a clear order of "good guys versus evil empire," and the US was as likely to be portrayed as a meddling imperialist as it was a hero. As "X-Files" creator Chris Carter once mused, Mulder and Scully, the TV show's main characters, "are equal parts of my desire to believe in something and my inability to believe in something. My skepticism and my faith."

The coolly ironic mood of the 1990s appears to have given way today to a harsher brand of conspiracy theorizing, hardened by a world where, in the case of drones, the US government seems to have openly adopted an assassination program.

The Internet, moreover, has provided a megaphone for voices on the fringe. On one hand, it gives Americans access to unprecedented amounts of information. But the result has sometimes been a factual dystopia, in which people sift the Internet for opinions that justify their own.

Going too far?

The danger is "taking that story and reducing it to some deeply antisocial and dangerous way of explaining the world," says Professor Fenster of the University of Florida.

An April poll by Public Policy Polling of Raleigh, N.C., gives some evidence of that. Some 17 percent of voters "said they think a group of world bankers are slowly eliminating paper currency to force most banking online – only to cut the power grid so regular citizens can't access money and are forced into worldwide slavery."

Hard facts rarely, if ever, stop a conspiracy. Contradictory evidence is either ignored or seen as a sign of counterconspiracy.

In the aftermath of the Newtown, Conn., massacre in 2012, conspiracy theorists used a short film of a shotgun being taken out of a car and an incorrect report that the perpetrator had not used an assault-style Bushmaster rifle to suggest an elaborate federal plot to ban high-powered firearms. Never mind that the school was riddled with holes and .223 bullet casings and rounds that match those fired from a Bushmaster.

Another theory purports that the massacre never happened, that all the victims were actors who somehow managed to fool a community inundated with hundreds of reporters.

Modern conspiracy theories have the whiff of "truthiness," a term invented by Comedy Central comedian Stephen Colbert, meaning that a basic template of potentially nefarious connections can be laid over almost any event.

The universality of that construct means that conspiracy theories can have a broad appeal. "I don't think that people who believe in conspiracy theories have some kind of mental pathology," says Michael Barkun, a law professor at Syracuse University and the author of "A Culture of Conspiracy: Apocalyptic Visions in Contemporary America." "In fact, it's the very ordinariness of people who believe in conspiracy theories that makes the phenomenon a troubling one."

Meanwhile, the Internet has given voices once on the fringe of society a larger forum.

"What happened is that people who had been in isolated conspiracy subcultures are now in a position to communicate their beliefs to a very large audience, and as a result what you get is the mainstreaming of fringe," Professor Barkun says. "The spread of it leads people to think a couple of things: One, that appearances are meaningless, that somehow the real decisions are being made behind the scenes, and, secondly, that the real decisionmakers are invisible [while] pulling the strings."

Sometimes, events seem to corroborate those views. The leaks by former National Security Agency contractor Edward Snowden, for example, suggest that fears about government snooping have at least some basis in reality.

"When things come to light like the NSA activity, it appears to validate conspiracy theories, although obviously there's a big difference between the NSA revelations and new world order conspiracy theories," Barkun adds.

Some quests lead to real answers

Yet the search for the "truth out there" occasionally leads to new answers, even if they don't fit neatly into a conspiracy.

Demands for the Feds to fess up about Area 51, an alleged secret government site of human-alien interaction, finally led to the release earlier this year of papers confirming that the CIA was testing peculiar-looking flying machines.

And in his video short "The Umbrella Man" about the Kennedy assassination, filmmaker Errol Morris deconstructs the story of the man who raised an umbrella near the Kennedy motorcade, ostensibly a signal and thus proof of a broader conspiracy. Mr. Morris ends the short by quoting testimony by the Umbrella Man, Louie Steven Witt, who told Congress that the umbrella was intended to heckle Kennedy, whose father, Joe Kennedy, had supported British Prime Minister Neville Chamberlain, who was later criticized for appeasing the Nazis. (Chamberlain usually carried an umbrella.)

The quest for meaning in the 486-frame Zapruder film footage is evidence that the Kennedy assassination "has produced this epistemic war of people battling for reality ... trying to wrest control back from chaos," as Morris told Smithsonian Magazine.

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The resonance of modern conspiracy, 50 years later, still pulls Americans back to that sunny fall day in Dallas, when Oswald shattered a postwar "age of innocence."

"Is it more likely that Lee Harvey Oswald was a frustrated human being, a failure at everything he ever tried, desperate for attention, and not in his right mind, and that he took a gun to his place of work one day and shot a president who was riding in an open limousine?" wonders Professor Cunningham at Texas Tech. "Or is it more believable that Oswald was a patsy of the CIA, which was working with the mafia, which had ties to Lyndon Johnson and ... Fidel Castro, to completely, and in all quiet, murder a president and cover it up in front of hundreds of onlookers?"