19 outlandish conspiracy theories Donald Trump has floated on the campaign trail and in the White House

Many wanted a response from Trump, who had just watched President Obama deliver jokes that night about Trump's constant questioning of the legitimacy of Obama's birth certificate.

Years later, Trump is still not convinced of the legitimacy of Obama's birth certificate. But this was perhaps the first of numerous debunked or unverified conspiracy theories that Trump has entertained during his time in the political spotlight.

Throughout the 2016 campaign and while in the White House, Trump has floated theories fueled by the conspiratorial-minded corners of supermarket tabloids and the internet, something unprecedented in modern politics. He's often used them as weapons against his opponents.

Here are some of the most notable conspiracy theories Trump has entertained:

Questions about Ted Cruz's father's potential ties to President John F. Kennedy's assassin.

On the eve of the Indiana primary, Trump attempted to undermine former Republican presidential rival Ted Cruz's father's legitimacy by parroting an unverified National Enquirer story.

It claimed Rafael Cruz was photographed in the early 1960s handing out pro-Fidel Castro leaflets with President John F. Kennedy's assassin, Lee Harvey Oswald.

The Cruz campaign denounced the piece as "garbage."

Questions about President Obama's birth certificate.

While mulling a potential 2012 presidential bid, Trump became the most high-profile figure to promote the rumors suggesting that President Obama was not born in the US.

Trump claimed he'd deployed private investigators who "could not believe what they're finding" about Obama's place of birth.

He also repeatedly clashed with reporters who pushed him on the issue. During one contentious interview, he told ABC's George Stephanopoulos that he'd been "co-opted" by "Obama and his minions" when the anchor tried to push back on Trump's claims.

When Obama eventually released his long-form birth certificate, Trump questioned the document's authenticity.

Trump has since continued to push the conspiracy theory in recent months during his presidency, according to advisors who spoke with the New York Times. One sitting US senator echoed these reports.

Questions about a former Bill Clinton aide's suicide.

After Vince Foster, a former aide to President Bill Clinton, was found dead in 1993, various law-enforcement agencies and independent counsels determined he committed suicide.

But Foster's death spawned conspiracy theorists who questioned whether the Clintons themselves were involved in Foster's death.

In an interview with The Washington Post, Trump suggested Foster's death was "very fishy."

"He had intimate knowledge of what was going on," Trump said of Foster's role in the White House. "He knew everything that was going on, and then all of a sudden he committed suicide."

He added: "I don’t bring [Foster’s death] up because I don’t know enough to really discuss it. I will say there are people who continue to bring it up because they think it was absolutely a murder. I don’t do that because I don’t think it’s fair."

Questions about whether Syrian refugees are ISIS terrorists.

Trump has, in part, justified his plan to temporarily bar Muslim immigrants from entering the US by claiming that refugees coming from Syria "could be a Trojan horse."

"It could be one of the greatest coups of all time," Trump told Fox News' Sean Hannity last year. "They could be ISIS. It could be a plot. I mean, I don't want to think in terms of conspiracy, but it could be a plot."

But the process for vetting refugees typically lasts 18 to 24 months, and immigration experts maintain it is one of the most difficult ways for terrorists to attempt to enter the US legally.

"It is extremely unlikely that someone who is a terrorist will be sent through the refugee resettlement program," Greg Chen, the director of advocacy at the American Immigration Lawyers Association, told Business Insider.

He added: "It takes a great deal of time, and it wouldn't make sense for someone who is a terrorist for someone to go through that process. There are going to be easier ways for a terrorist to try to infiltrate, rather than going through the refugee resettlement program."

Questions about whether an ISIS-linked terrorist attempted to charge at Trump on stage.

After an attendee at Trump's March 2016 rally in Dayton, Ohio, attempted to charge the stage, Trump claimed a video he retweeted proved the attendee was a terrorist linked to ISIS.

"He was playing Arabic music. He was dragging the flag along the ground, and he had internet chatter with ISIS and about ISIS. So I don't know if he was or not," Trump said. "But all we did was put out what he had on his internet. He's dragging the flag, the American flag, which I respect obviously more than you."

He added: "What do I know about it? All I know is what's on the internet. And I don't like to see a man dragging the American flag along the ground in a mocking fashion."

Multiple news outlets and fact-checkers debunked the video's authenticity. No government agency has said the man was connected to ISIS or other terrorist groups.

Questions about Supreme Court Justice Antonin Scalia's death.

Law enforcement determined there was no evidence of foul play in Justice Antonin Scalia's sudden death this year.

Asked about the circumstances of Scalia's death, Trump said he was unsure about what caused Scalia's death. Trump noted a pillow was found over the justice's face, a claim authorities rebutted.

"I'm hearing it's a big topic," Trump said in a radio interview. "It's a horrible topic but they're saying they found the pillow on his face, which is a pretty unusual place to find a pillow."

He added: "I can't give you an answer. It's just starting to come out now."

Questions about whether childhood vaccines cause autism.

At a Republican presidential debate in 2016, CNN host Jake Tapper asked Trump about his position that vaccines can cause autism.

"We had so many instances, people that work for me, just the other day, 2 years old, a beautiful child, went to have the vaccine and came back and a week later got a tremendous fever, got very, very sick, now is autistic," Trump said.

Shortly after Trump's assertion, former presidential candidate and neurosurgeon Ben Carson corrected the real-estate mogul, pointing out that overwhelming medical evidence suggests that there's no link between autism and vaccines.

A 2013 study from the Centers for Disease Control and Prevention found no connection between vaccines and an increased risk of autism.

Questions about whether Muslims in New Jersey were cheering after 9/11.

For weeks last year, Trump emphatically claimed he saw televised news reports of Muslims cheering in New Jersey after the September 11, 2001, terrorist attacks.

"There were people that were cheering on the other side of New Jersey, where you have large Arab populations. They were cheering as the World Trade Center came down," Trump said during an ABC interview.

He added: "I know it might be not politically correct for you to talk about it, but there were people cheering as that building came down — as those buildings came down. And that tells you something. It was well-covered at the time."

However, there is no evidence to suggest there were any American celebrations aired on television following the attacks. Some media reports at the time cited rumors of celebrations in New Jersey. But reports were never substantiated, and there's no evidence these protests were broadcast on national television.

Questions about whether wives of 9/11 hijackers fled to Saudi Arabia before the attacks.

The presumptive Republican presidential nominee repeatedly stated last year that the terrorists who carried out the September 11, 2001, attacks moved their families out of the US to Saudi Arabia several days before the hijacking.

"When you had the World Trade Center go, people were put into planes that were friends, family, girlfriends, and they were put into planes and they were sent back, for the most part, to Saudi Arabia," Trump said. "They knew what was going on. They went home and they wanted to watch their boyfriends on television."

The 9/11 commission report, the most extensive investigation into the events surrounding the attacks, determined that few of the hijackers kept in contact with their families, and none had family members living in the US.

PolitiFact also called the claim false.

Questions about the legitimacy of climate change.

Though many Republican leaders remain skeptical of climate change, Trump has taken his skepticism a step further. In 2012 he suggested that climate change is a "total, and very expensive hoax" perpetuated by China's government.

"The concept of global warming was created by and for the Chinese in order to make U.S. manufacturing non-competitive," Trump tweeted in 2012.

Trump backed off the tweet, telling Fox News in January that his comment was a "joke." Still, the real-estate mogul has repeatedly maintained that climate change was a hoax, and said climate-change studies are "done for the benefit of China."

According to NASA, 97% of publishing climate scientists believe that human activities such as burning of fossil fuels have caused climate change.

Questions about whether asbestos is a "great con."

In a 1992 interview with New York magazine, Trump suggested the mob's "strong lobby" in New York may be responsible for asbestos.

"One of the great cons is asbestos," Trump said. "There's nothing wrong except the mob has a strong lobby in Albany because they have the dumps and control the truck."

Trump has more recently embraced the reality.

Last year, the real-estate mogul cited how he increased the valuation of one of his properties by millions after embarking on a massive asbestos-removal operation.

Questions about Marco Rubio's presidential eligibility.

Trump has a long history of speculating whether potential presidential rivals are constitutionally eligible to serve.

In February, the former reality-TV star retweeted a supporter who claimed Rubio was ineligible to run because his parents were not natural-born US citizens, a claim that no major constitutional experts support.

When confronted on ABC's "This Week" about whether he believed Rubio was not constitutionally permitted to occupy the presidency, Trump, whose mother was born in Scotland, refused to disavow the tweet.

"I've never looked at it, George," Trump said of the tweet. "I honestly have never looked at it. As somebody said, he's not. And I retweeted it. I have 14 million people between Twitter and Facebook and Instagram, and I retweet things and we start dialogue and it's very interesting."

He added: "I'm not sure. Let people make their own determination."

Questions about Fox News being owned by a Saudi billionaire.

Trump's war with Fox News' Megyn Kelly recently reached a detente.

But during the peak of Trump's rhetorical battle with Kelly, he perpetuated a prominent outlandish theory from one of his Twitter followers.

In January, the real-estate mogul retweeted a photo purportedly showing Saudi billionaire Prince Alwaleed bin Talal with Kelly. The photo claimed the prince was a partial Fox News owner, which multiple outlets found was untrue. Alwaleed's investment company owns a small share of 21st Century Fox.

Questions about the legitimacy of the "Access Hollywood" tape

Toward the tail end of his presidential campaign, the 2005 "Access Hollywood" tape featuring Trump apparently admitting that he likes to grab women "by the p----" received broad coverage, and Trump apologized for his comments shortly afterward.

More recently though, after various allegations of sexual harassment in media and politics have begun to surface, Trump has walked back these comments.

“We don't think that was my voice,” Trump reportedly told a senator, according to The New York Tiimes.

The Times' sources did not elaborate on why Trump has begun to doubt the authenticity of the tape's audio.

Claims that Joe Scarborough killed one of his interns

In a tweet Trump sent Wednesday morning, he made references to a conspiracy theory that claims MSNBC anchor Joe Scarborough of "Morning Joe" murdered one of his staffers in Florida in 2001.

While Scarborough was serving as a Republican congressman in Florida's 1st district, one of his interns,

Claims that Obama had wiretapped Trump's phone

In March 2017, Trump sent a tweet accusing Obama of wiretapping his phones in Trump Tower.

PolitiFact and other outlets have debunked the claim. An Obama spokesman also issued a response to the allegation, saying:

Claims that voter fraud in the 2016 election cost him the popular vote

In a tweet sent shortly after the November 2016 election, Trump wrote:

This unsubstantiated claim was repeated by Kris Kobach, the chairman of Trump's panel on voter fraud, in July. The fact-checking site Snopes has debunked the claim entirely, citing "zero evidence."

Retweeting anti-Muslim conspiracy videos

In November 2017, Trump caused diplomatic havoc by retweeting three videos posted by Jayda Fransen of the ultra-nationalist, anti-Muslim organization Britain First that purportedly showed Muslims in Europe committing crimes and destroying Christian icons.

Britain First has frequently targeted mosques and Muslims in the UK in order to brand all Muslims as violent extremists, and Trump's retweet of the videos was widely seen as a tacit endorsement of the group's efforts.

Although the authenticity of the videos has been called into question, White House press secretary Sarah Huckabee Sanders has maintained this doesn't matter.

Claims 3,000 people didn't die in Puerto Rico after Hurricane Maria and that Democrats inflated the death toll.

In a tweet on Thursday morning, Trump claimed 3,000 people didn't die in Puerto Rico after Hurricane Maria and accused Democrats of inflating the death toll to make him "look as bad as possible," rejecting the findings of a government-funded study in the process.

said

A study commissioned by the Puerto Rico government that was released in August found that 2,975 people died in the wake of the storm.

Trump has been widely criticized for his response to Hurricane Maria, particularly by

19 outlandish conspiracy theories Donald Trump has floated on the campaign trail and in the White House

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