7 times Donald Trump made false or unsubstantiated claims

— -- President Donald Trump faced criticism this week over claims he made about two separate phone calls: one with the leader of the Boy Scouts of America and another with the president of Mexico.

The president's seemingly untruthful statements join a list of his previous ungrounded claims, coming as he consistently reprimands the media for what he interprets as dishonesty in stories covering his administration

Trump is no stranger to pushing falsehoods or unsubstantiated claims. Here are some examples:

Obama birtherism theory

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

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

“President Barack Obama was born in the United States, period,” Trump said. “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."

Claims of ‘serious voter fraud’ in 2016 election

Even after he won the election, Trump continued to insist that voter fraud occurred -- that he would have won the popular vote if not for "millions of people who voted illegally," but provided no evidence to support the claim.

Clinton won the popular vote by nearly 3 million ballots.

In December, Vice President-elect Mike Pence, defended Trump, citing a Pew study as the source for the "millions" who allegedly voted illegally.

But the Pew study's primary author, David Becker, tweeted in response to references to his research: "As primary author of the report the Trump camp cited today, I can confirm the report made no findings re: voter fraud. We found millions of out of date registration records due to people moving or dying, but found no evidence that voter fraud resulted. Voter lists are much more accurate now than when we issued that study in 2012, thanks to the 20 states sharing data through @ericstates_info."

In another tweet, Trump named Virginia, New Hampshire and California as three states with "serious voter fraud." There is no evidence to back up the claim, and it's unclear why those states were singled out.

ABC News reached out to election officials in all 50 states shortly before Election Day and not one had any evidence or reason to believe that widespread voter fraud has or would occur in their states.

Obama founded ISIS

At an August rally in Florida, Trump told supporters that President Obama is the "founder of ISIS."

"ISIS is honoring President Obama," he said. "He is the founder of ISIS. He founded ISIS. And I would say the co-founder would be crooked Hillary Clinton."

He pulled back on those comments two days later, saying they were "sarcasm."

The terrorist group can trace its history back to 2000 in Iraq. The group become known as ISIL in June 2014 with its founder Abu Bakr al-Baghdadi declaring it had established an Islamic "caliphate" in Iraq and Syria.

9/11 celebrations

During the campaign, then-Republican contender Trump claimed residents of Jersey City, N.J., celebrated the World Trade Center attacks, telling ABC News' George Stephanopoulos that "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 that 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 Trump's remarks. Trump continued to stand by the assertion for weeks, even though no media outlet uncovered 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, 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 Kennedy's killer, just three months before the assassin.

On "Fox and Friends," Trump seized on the claim, 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 lashed out at his son’s then-GOP rival.

"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.” "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."

U.S. intelligence community leaked dossier

Trump has suggested the intelligence community was involved in leaking the unverified dossier that include salacious allegations about Trump and his connections to Russia.

In January, Trump tweted "Probably...released by "Intelligence" even knowing there is no proof, and never will be."

Trump pointed the finger at outgoing-CIA Director John Brennan in response to an interview Brennan gave to Fox News.

"Oh really, couldn't do much worse - just look at Syria (red line), Crimea, Ukraine and the build-up of Russian nukes. Not good! Was this the leaker of Fake News?" Trump tweeted in response to Brennan's assessment that Trump did not have a "full appreciation" of the threat of Russia.

In his interview on "Fox News Sunday," Brennan said that "there is no basis for Mr. Trump to point fingers at the intelligence community for leaking information that was already available publicly."

Director of National Intelligence James Clapper also said in a statement released last week that he believes the leaks did not come from the intelligence community.

"We also discussed the private security company document, which was widely circulated in recent months among the media, members of Congress and Congressional staff even before the IC became aware of it. I emphasized that this document is not a U.S. Intelligence Community product and that I do not believe the leaks came from within the IC," the statement read.

Clapper said the document was created by a private security company and "widely circulated in recent months among the media, members of Congress and Congressional staff even before the IC became aware of it."

Phone calls with Boy Scouts, Mexican president

During an interview with The Wall Street Journal last week -- a full transcript of which was later published by Politico -- Trump was steadfast in his claim that his speech at the Boy Scouts' National Jamboree in West Virginia was universally well-received, telling the reporter that he "got a call from the head of the Boy Scouts saying it was the greatest speech that was ever made to them."

The statement was quickly refuted by the organization, which released a statement saying it was unaware of any such call.

When asked about Trump's description of the call at Wednesday's press briefing, press secretary Sarah Sanders said only that “multiple members of the leadership following his speech there that day congratulated him, praised him and offered quite … powerful compliments following his speech.”

Earlier in the week, Trump said in a cabinet meeting that he was "called" by Mexican President Enrique Pena Nieto and told "very few people are coming [across the U.S. southern border] because they know they’re not going to get through our border."

Later that day, Mexico’s secretariat of foreign affairs said Nieto "has not had recent communication via telephone with President Donald Trump," though he noted the two leaders spoke in person during last month's G-20 summit.

Sanders later indicated that the conversation took place in-person, despite Trump's claim of a phone call.

ABC News’ Katherine Faulders, Adam Kelsey and Ryan Struyk contributed to this report.