Sen. Ted Cruz's father had a role in John F. Kennedy's murder. President Obama is Muslim and fabricated his birth certificate. 1970s radical/domestic terrorist Bill Ayers is the real author of Obama's memoir "Dreams From My Father." Supreme Court Justice Antonin Scalia might have been murdered. Liberals are trying to ban Christmas. Climate change is a hoax pushed by the Chinese government.

These are a few of the many conspiracy theories Republican presidential nominee Donald Trump has advanced. The latest, just this week: he said Democratic nominee Hillary Clinton helped former Miss Universe Alicia Machado -- who Trump famously called "Miss Piggy" -- gain citizenship so she could vote against him. He then told his Twitter followers to go check out Machado's sex tape, which doesn't exist.

These wild charges might make you chuckle, but they're no laughing matter. A lot of Americans believe them to be true. Historian Deborah E. Lipstadt, an expert on the Holocaust denial movement, insists we're living in a golden age of conspiracy theories that is undermining our democracy, the country's cohesiveness and scientific progress.

The internet bears a large measure of blame. Social media increasingly walls us off from unwanted viewpoints and news, reinforcing biases and misconceptions.

But the mainstreaming of nutty theories began long before the web took over the world. Conspiracy theorists gained traction in the 1970s and '80s when they started to mimic honest seekers of truth. Holocaust deniers, Lipstadt told Time magazine, led the charge:

"In the mid-'70s the deniers changed their M.O. and they did something, which is not uncommon among conspiracy theorists today and among extremist groups today, where they still held the same beliefs as before, but their outer presentation became much more academic-like," she said. "They began to publish books with footnotes. They began to hold conferences. They began to show up on television where they were often given a voice. But instead of looking like neo-Nazis, dressed in stormtrooper uniforms, they began to talk in a very measured way about how the documents showed that [the Holocaust] was impossible."

This was the perfect approach for the time, an era when reading as a pastime was falling as more and more people gained most of their information from television. (Trump admits he doesn't read much, that he doesn't have the time. But he "hears things.")

Lipstadt says the inspiration for this new M.O. came from a legitimate, if controversial, academic movement: deconstructionism. This abstract discipline, popularized in the 1960s and '70s by the late French philosopher Jacques Derrida, subverts the intended meaning of texts and even words themselves.

If you embrace deconstructionism, Lipstadt points out, "you can look at a document and interpret it in any way you wish."

This, of course, is perfect for conspiracy theorists, allowing them to build fanciful interpretations of evidence that have little relationship to the original facts. Climate-change skeptics sometimes use deconstructionist tricks to give their pseudo-scientific work the sheen of credence.

"I think we're living at a time when conspiracy theorists and people with outlandish ideas that do not correspond to the facts are finding more of a fertile field, more of a welcome, more of an ability to promulgate their claims than we've ever had before," Lipstadt said.

The 2016 presidential election is proving that Lipstadt's fears are justified. Americans just might elect a determined conspiracy theorist to the highest office in the land, and if they don't, Donald Trump has already primed the pump for conspiracy theories that explain why he failed.

"The only way we can lose, in my opinion, I really mean this, Pennsylvania," Trump said at a rally in August, "is if cheating goes on."

-- Douglas Perry