5 conspiracy theories Trump has promoted over the years

— -- President Donald Trump has a history of casually repeating what he hears or reads, some of which fall into the realm of conspiracy theories.

He is also now, sources told ABC News, privately questioning the authenticity of the 2005 "Access Hollywood" video in which he made vulgar comments about women, and, according to The New York Times, continues to question former President Obama's birthplace. The about-face comes months after he apologized for his remarks on the tape and also rejected his years-long skepticism of Obama's citizenship.

Here is a review of five of the most persistent and latest theories Trump has promoted.

Obama birtherism theory

Trump perpetuated the myth for years that Barack Obama was not born in the United States, often using tweets to push the claim, starting in 2011.

Despite the president’s releasing his long-form birth certificate in 2011, Trump only conceded at a Sept. 16, 2016, news conference used to promote his new Washington, D.C., hotel that Obama was born in the United States.

“President Barack Obama was born in the United States, period,” Trump said then. “Now we all want to get back to making America strong and great again.”

Born in Hawaii in 1961, Obama released his short-form birth certificate from the Hawaii Department of Health in 2008. He released his long-form birth certificate in 2011, saying he "believed the distraction over his birth certificate wasn’t good for the country."

But that didn't stop Trump from continuing to cast doubt, based on U.S. law that only a "natural born Citizen, or a Citizen of the United States, at the time of the Adoption of this Constitution, shall be eligible to the Office of President."

Even after publicly putting his birther claims to rest in 2016, Trump offered no apology for the years he had prompted the myth, instead taking credit for what he portrayed as his putting an end to any uncertainty over the president's place of birth.

Trump also made a claim in that same speech, which has been proven false, that Clinton and her 2008 campaign started the birther movement when she was running against then-Sen, Obama for the presidency.

"Hillary Clinton and her campaign of 2008 started the birther controversy. I finished it," Trump said on Sept. 16, at the end of a 20-minute event promoting his new hotel.

Most recently, The New York Times reported Tuesday that Trump has been having closed-door conversations where he questions the validity of his predecessor’s birth certificate. https://www.nytimes.com/2017/11/28/us/politics/trump-access-hollywood-tape.html?_r=1

9/11 celebrations

Then-Republican contender Trump said during the campaign that some residents of Jersey City, New Jersey, celebrated the World Trade Center attacks, telling ABC News' George Stephanopoulos "there were people that were cheering on the other side of New Jersey where you have large Arab population."

"They were cheering as the World Trade Center came down," 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."

At a campaign event the next day, he doubled down on the assertion.

"Lo and behold I start getting phone calls in my office by the hundreds, that they were there and they saw this take place on the internet," Trump said in Ohio.

At the time, several of Trump's fellow GOP candidates, including Jeb Bush and Marco Rubio, condemned the remarks. But Trump continued to stand by the assertion for weeks, even though no media outlet found any reports from the time, nor did Trump’s campaign provide any evidence to confirm that “thousands and thousands” of Muslims in New Jersey celebrated the Sept. 11 attacks.

ABC News checked all footage from the time of the attacks and the weeks after, finding no such claims or basis for the claims.

Ted Cruz's father allegedly involved in the JFK assassination

In May 2016, Trump latched on to an unsubstantiated claim in a National Enquirer report that Sen. Ted Cruz's father, Rafael Cruz, was caught on camera with Lee Harvey Oswald, President John Kennedy's killer, three months before the assassination.

On "Fox and Friends" on May 3, 2016, Trump seized on the allegation, saying, "I mean, what was he doing with Lee Harvey Oswald shortly before the death, before the shooting? ... It's horrible."

In an interview with ABC News’ Tom Llamas, Rafael Cruz denied the report and lashed out at his son’s then-GOP rival.

"It's ludicrous. It's ludicrous. I was never in New Orleans at that time," Rafael Cruz told ABC News.

"That's typical of Donald Trump -- just attack and make all kinds of innuendo and attacks with no substance,” the elder Cruz said.

But Trump stood by his unsubstantiated claim, citing only the National Enquirer article as his evidence.

"All I did was refer to it. I’m just referring to an article that appeared. It has nothing to do with me," he said on “Good Morning America” on May 4, 2016. "The National Enquirer gave you John Edwards. It gave you O.J. Simpson. It gave you many, many things. I mean, you can’t knock the National Enquirer. It’s brought many things to light."

Questioning the authenticity of the "Access Hollywood" tape

Despite apologizing months ago for the infamous 2005 "Access Hollywood" recording of his vulgar comments about women, President Donald Trump is now privately questioning the authenticity of the video capturing his exchange with television host Billy Bush, according to sources.

The confirmation that Trump has raised doubts about the video to advisers in recent weeks stands in contrast to at least two instances in which he discussed the video’s content without denying it or raising questions about its veracity.

Hours after the 2005 recording was released Oct. 7, 2016, then-candidate Trump made his first public statement about the comments, in which he said "when you're a star" women let men "do anything," including "grab them by the p----."

"Anyone who knows me knows these words don't reflect who I am. I said it, I was wrong and I apologize," Trump said in a video statement he released on his social media accounts that evening.

He said at another point in the video, "I never said that I'm a perfect person, nor pretended to be someone that I'm not.”

He was also questioned about the tape during the presidential debate days after release of the tape.

"I’ve said things that, frankly, you hear these things I said. And I was embarrassed by it. But I have tremendous respect for women," Trump said during the debate.

Intern's death in Joe Scarborough's office

Trump urged his followers to "investigate" the 2001 death of a woman who worked as a congressional aide to then-Rep. Joe Scarborough, R-Fla.

Scarborough now hosts MNSBC's "Morning Joe" and has been a frequent target of Trump's ire both during the campaign and his presidency.

The 2001 incident, in which aide Lori Klausutis was found dead in Scarborough's congressional office, has been raised by conspiracy theorists and bloggers in the past.

"So now that Matt Lauer is gone when will the Fake News practitioners at NBC be terminating the contract of [MSNBC president] Phil Griffin? And will they terminate low ratings Joe Scarborough based on the “unsolved mystery” that took place in Florida years ago? Investigate!" Trump wrote today.

According to the St. Petersburg Times, which covered Klausutis' death in 2001, the medical examiner reported that the then-28-year-old aide lost consciousness because of an abnormal heart rhythm and fell, hitting her head on a desk, which caused her death, the paper reported.

Kluasutis had told two people the day before her body was found that she had not been feeling well, according to the police report.