 -- President Donald Trump on Thursday signed an executive order to form a task force that will review alleged voter fraud, improper voter registrations and “election integrity” in the federal election system -- an issue that has long been a concern of the president, during the campaign and after.

Trump and the White House have reiterated the false assertion that millions of people illegally cast ballots in the 2016 presidential election -- a claim Trump first made just weeks after the election without presenting evidence.

And then in late January, Trump referenced claims made by blogger Gregg Phillips, founder of VoteStand and a board member of the controversial voter fraud watchdog True the Vote.

In an interview with CNN that aired on Jan. 27, 2017, Phillips claimed that: “More than three million non-citizens voted in this country in this election. We're prepared to prove it. We need a little more time. We believe that it will probably take another few months to get this done." Phillips has offered no such proof.

White House Press Secretary Sean Spicer said at that time that President Trump "does believe that" millions of illegal votes were cast in the presidential election -- citing "studies and information" that were presented to him as the basis of this belief. Spicer said "maybe we will" investigate the claimed fraud.

What Evidence Do We Have of Voter Fraud in the 2016 Election?

Academic experts and election officials say there was no evidence of any widespread voter fraud in the 2016 presidential race.

A study published last week and a new study by the Brennan Center for Justice at the NYU School of Law found only 30 incidences of noncitizen voting out of 23.5 million votes casts in select jurisdictions with the highest populations of non-citizens. That means just 0.0001 percent of votes were cast by people who are not American citizens, according to the study authors.

Similarly, in Ohio -- where election officials have been vigilant about uncovering non-citizen voting -– a study published in February 2017 by the Ohio Secretary of State found just 126 cases of non-citizens who illegally voted since 2010 out of more than 15 million total votes cast, or about 0.00001 percent of cast votes. The office identified just 7 cases from the 2016 general election.

"We are not aware of any evidence that supports the voter fraud claims made by President Trump, but we are open to learning more about the Administration’s concerns," the National Association of Secretaries of State said in January in a statement. "In the lead up to the November 2016 election, secretaries of state expressed their confidence in the systemic integrity of our election process as a bipartisan group, and they stand behind that statement today.”

What We Know About The Evidence Spicer Cited in January

Spicer defended Trump's unsubstantiated assertions of millions of illegal votes by citing an academic study. "There’s one that came out of Pew in 2008 that showed 14 percent of people who voted were non-citizens," he said.

It's true there was a Pew Charitable Trusts study released in 2012 -- not 2008 -- that focused on voter registration irregularities, not actual voter fraud. That study found that approximately 24 million voter registrations were invalid or significantly inaccurate, more than 1.8 million deceased individuals were listed as voters and approximately 2.75 million people had registrations in more than one state. But the study's author, David Becker, wrote on Twitter that researchers found “no evidence that voter fraud resulted” from the irregularities on the voter registration books.

As I've noted before, voting integrity better in this election than ever before. Zero evidence of fraud. https://t.co/BBS8NVcACB — David Becker (@beckerdavidj) January 24, 2017

But the statistic Spicer cited comes from a report from two Old Dominion University professors in a 2014 Electoral Studies article, not from Pew. Spicer misrepresented that statistic: the study claimed 14 percent of non-citizens thought they were registered to vote -- not that they had actually cast ballots in the election. The study, written by professors Jesse Richman and David Earnest, found that at most 6.4 percent of non-citizens may have voted. But the study’s methodology –- using data from an online survey -- has faced broad criticism from the academic community.

Richman has told ABC News that his findings have been “taken out of context” and should not be used “to make an unsupported claim concerning massive vote fraud.” "I don’t know if Trump has read our statements to try to set the record straight. If he has, he’s deliberately trying to mischaracterize what our study shows," Richman told ABC News today.

"Did the non-citizen vote lead to Trump’s popular vote loss? No. Our data doesn’t support that," he told ABC News.

What Experts Say About Voter Fraud in the United States

Experts don't claim that voter fraud is impossible or never happens. But it is very rare -- in most instances only concerning individual ballots.

"The scale he's talking about is just simply absurd," Lorraine Minnite, a professor at Rutgers who specializes in voter fraud research, told ABC News in January. "There have been a handful of cases where people who are not citizens have made it onto the voter rolls for various reasons ... but the idea that 3 to 5 million illegal voters successfully cast ballots that were counted in this election is just beyond belief."

The Lawyers’ Committee for Civil Rights Under Law -- which led Election Protection, the nation’s largest non-partisan voter protection program -- called Trump’s fraud claims “bombastic” and “contrary to the evidence amassed this election cycle" when he first made them in November.

Even True the Vote -- a controversial advocacy group that mines for examples of voter fraud -- claimed they have discovered only 1,264 "voter crime" convictions in the last two decades, the result of a year of exhaustive research of state and local records.

These "voter crime" convictions weren’t exclusively voter fraud, but also included voter intimidation, vote buying and registration fraud.. And the "vast majority" of these crimes happened in state and local elections, according to True the Vote spokesman Logan Churchwell. Those 1,264 vote crimes are out of over a billion votes cast.

As I've noted before, voting integrity better in this election than ever before. Zero evidence of fraud. https://t.co/BBS8NVcACB

But the statistic Spicer cited comes from a report from two Old Dominion University professors in a 2014 Electoral Studies article, not from Pew. Spicer misrepresented that statistic: the study claimed 14 percent of non-citizens thought they were registered to vote -- not that they had actually cast ballots in the election. The study, written by professors Jesse Richman and David Earnest, found that at most 6.4 percent of non-citizens may have voted. But the study’s methodology –- using data from an online survey -- has faced broad criticism from the academic community.

Richman has told ABC News that his findings have been “taken out of context” and should not be used “to make an unsupported claim concerning massive vote fraud.” "I don’t know if Trump has read our statements to try to set the record straight. If he has, he’s deliberately trying to mischaracterize what our study shows," Richman told ABC News today.

"Did the non-citizen vote lead to Trump’s popular vote loss? No. Our data doesn’t support that," he told ABC News.

What Experts Say About Voter Fraud in the United States

Experts don't claim that voter fraud is impossible or never happens. But it is very rare -- in most instances only concerning individual ballots.

"The scale he's talking about is just simply absurd," Lorraine Minnite, a professor at Rutgers who specializes in voter fraud research, told ABC News in January. "There have been a handful of cases where people who are not citizens have made it onto the voter rolls for various reasons ... but the idea that 3 to 5 million illegal voters successfully cast ballots that were counted in this election is just beyond belief."

The Lawyers’ Committee for Civil Rights Under Law -- which led Election Protection, the nation’s largest non-partisan voter protection program -- called Trump’s fraud claims “bombastic” and “contrary to the evidence amassed this election cycle" when he first made them in November.

Even True the Vote -- a controversial advocacy group that mines for examples of voter fraud -- claimed they have discovered only 1,264 "voter crime" convictions in the last two decades, the result of a year of exhaustive research of state and local records.

These "voter crime" convictions weren’t exclusively voter fraud, but also included voter intimidation, vote buying and registration fraud.. And the "vast majority" of these crimes happened in state and local elections, according to True the Vote spokesman Logan Churchwell. Those 1,264 vote crimes are out of over a billion votes cast.