As Donald Trump reminded the world Tuesday morning, the Republican Party is on the verge of nominating a conspiracy theorist who regularly uses debunked Internet and tabloid rumors to smear his enemies.

In the latest case, Trump seized on a ludicrously thin-sourced National Enquirer story to insinuate Sen. Ted Cruz’s father, Rafael Cruz, was involved in the 1963 assassination of President John F. Kennedy.

“His father was with Lee Harvey Oswald prior to Oswald’s being, you know, shot,” Trump told Fox News over the phone. “I mean, the whole thing is ridiculous. What is this, right prior to his being shot, and nobody even brings it up. They don’t even talk about that. That was reported, and nobody talks about it.”

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Trump’s evidence? A photo, disseminated in fringe circles online and then by the National Enquirer, that conspiracy sleuths claim shows the elder Cruz near Oswald. There is zero evidence the person in question is Rafael Cruz.

“This man is a pathological liar,” Ted Cruz told reporters in response. “He doesn’t know the difference between truth and lies. He lies practically every word that comes out of his mouth. And in a pattern that I think is straight out of a psychology textbook, his response is to accuse everyone else of lying.”

Close video Ted Cruz launches seething attack on Donald Trump On the day of Indiana’s primaries, Republican presidential candidate Ted Cruz is not holding back. He lays into front-runner Donald Trump on infidelity, STDs, his bullying of women and more. On the day of Indiana’s primaries, Republican presidential candidate Ted Cruz is not holding back. He lays into front-runner Donald Trump on infidelity, STDs, his bullying of women and more. share tweet email Embed

Cruz has a point. Even by normal political standards, Trump’s relationship with the truth is abusive: Politifact named his entire campaign its 2015 “Lie of the Year.”

The GOP presidential front-runner, whether by choice or by nature, appears fundamentally unable to distinguish between credible sources and chain e-mails.

Equally significant, though, is that he uses these falsehoods to elevate fringe conspiracy theories and anecdotes that politicians are normally careful to keep far away from mainstream politics. He’s spread discredited claims linking vaccines to autism, for example — a debunked theory that medical officials say has harmed efforts to wipe out preventable diseases.

Trump has an online fan base of white nationalists, whom he sometimes retweets to his millions of followers. It’s important to note that many of the most egregious examples of Trump’s false claims have a strong racial and ethnic component.

Tuesday’s JFK story was a perfect example: A smear whose effect was to make Ted Cruz and his Cuban-born father appear strange, foreign, and untrustworthy. There are many others.

Birtherism

Before Trump ran for president, the most notorious example was his obsessive quest to prove President Obama hadn’t been born in the United States, thus making him ineligible to be president. Perpetuating the conspiracy theory that Obama had been born in Kenya, Trump boasted he would dispatch investigators to Hawaii, the president’s birthplace, to uncover the truth. The story got so out of control that Obama released his long form birth certificate in April 2011, confirming what the evidence already clearly demonstrated: That he was born in Honolulu in 1961.

Trump has focused less on the issue during his 2016 campaign, but has indicated he still is unsure of the president’s birthplace.

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Delving into another popular conspiracy theory on the fringe right, however, Trump has regularly implied in recent months that Obama is a secret Muslim. Asked by NBC’s Chuck Todd in September whether he could accept a Muslim president, Trump responded that, “some people have said it already happened, frankly.”

In February, Trump tweeted that Obama might have attended Justice Antonin Scalia’s funeral “if it were held in a Mosque.”

In both cases, Trump insisted when pressed that he wasn’t implying anything. As is often the case with Trump: He’s not sayin’, he’s just sayin’.

The Mexican ‘rapists’ conspiracy

Trump is well known for his tough stance on illegal immigration, which includes a pledge to deport all 11 million undocumented immigrants by force and build a border wall.

Underlying Trump’s position, though, is a fact-free conspiracy theory that charges the Mexican government with deliberately sending “rapists” and other criminals to the United States.

“The Mexican government forces many bad people into our country because they’re smart,” Trump told NBC News last July. “They’re smarter than our leaders, and their negotiators are far better than what we have, to a degree that you wouldn’t believe. They’re forcing people into our country. … And they are drug dealers and they are criminals of all kinds.”

Trump repeats these claims often, but has presented no evidence besides vague allusions to conversations with “border control people.”

Trump repeats these claims often, but has presented no evidence besides vague allusions to conversations with “border patrol people.”

Politifact awarded him a “pants on fire” for the claim, and even prominent advocates for a tougher border stance, like the Center for Immigration Studies, derided it as a myth.

Trump’s fantastical tales of a Mexican plot helped him sow fears that immigrants from that country are prone to violence, thus justifying extreme measures in response. In fact, migrants usually enter the U.S. seeking economic opportunity or fleeing human rights abuses, and studies suggest undocumented immigrants commit crimes at a lower rate than the general population.

The celebrating Muslims myth

In arguably the most outrageous case of Trump using lies and rumors to sow hatred and mistrust of a minority group, Trump denounced Muslim Americans as radicals and traitors with a story made out of whole cloth.

Last November, Trump implausibly claimed that he had personally witnessed “thousands and thousands” of Muslims celebrate the 9/11 attacks in New Jersey while watching television during the attacks.

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No such images were ever broadcast during the attacks and New Jersey officials denied seeing anything remotely resembling Trump’s claims, but rumors of celebrations persisted in part due to confusion over images that were widely televised of Palestinians in the West Bank. At most, an old MTV documentary offered anecdotal evidence of a handful of teens in Paterson who may or may not have been Muslim and may or may not have been celebrating the attacks at all.

Trump refused to concede the point, however, and continued to insist in an interview with ABC’s George Stephanopolous that he had seen the celebrations on TV and that the only reason it hadn’t been confirmed was that it wasn’t “politically correct.”

Phony crime statistics

Linking race, ethnicity, and crime is a recurring theme for Trump. Shortly after his claim about New Jersey Muslims, he retweeted fake statistics spread by white supremacists falsely claiming that black criminals disproportionately prey on whites.

Trump offered no apology afterward when pressed by Fox’s Bill O’Reilly about the racist image, and his answers gave valuable insight into what he considers legitimate sources of information.

“I retweeted somebody who was supposedly an expert and was also a radio show,” Trump said.

He added: “Am I going to check every statistic?”

General John Pershing’s apocryphal mass killings

Trump regularly regales his audience with a horrific tale about famed World War I-era General John Pershing subduing Muslim rebels in the Philippines by executing dozens of prisoners with bullets dipped in pig blood. Consuming pork is forbidden in Islam and the implication was that the blood would defile the bodies.

“He took 50 bullets, and he dipped them in pig’s blood,” Trump said at a rally in South Carolina in February. “And he had his men load his rifles and he lined up the 50 people, and they shot 49 of those people. And the fiftieth person he said ‘You go back to your people and you tell them what happened.’ And for 25 years there wasn’t a problem, okay?”

Historians said there was zero record of any of this mass execution ever happening, although there are accounts of soldiers burying fallen insurgents with pigs. The history was also completely wrong: Violence continued in the region long after the supposed story took place.

Once again, Trump’s source spoke volumes about his take on the truth. Snopes.com identified the Pershing story as a rumor spread by chain e-mails after the 9/11 attacks.

Trump still uses the anecdote regularly in his speeches.