Stephen Colbert has a one-word response to President Donald Trump’s claims about voter fraud: “bullshit.”

For months, Trump has been claiming that he only lost the popular vote in 2016 because “millions of people” voted illegally. He reiterated the argument during his Super Bowl interview with Fox News host Bill O’Reilly. “It’s really a bad situation,” Trump told O’Reilly. “It’s really bad.”

“This kind of accusation is called — and I don’t want to get too technical here — bullshit,” Colbert said.

The numbers for the 2016 election suggest there were four cases of reported voter fraud out of more than 138 million ballots cast. That’s far from Trump’s 3 million to 5 million estimate — and definitely not enough to make up for Trump’s popular vote deficit of about 2.8 million.

“Could be 4, could be 3 million,” Colbert said, pulling out a calculator to “split the difference.” “That adds up to … still bullshit.”

It’s not just Colbert who thinks Trump’s claims are baseless. Time and time again, researchers and journalists have looked into claims of widespread voter fraud. And time and time again, they’ve found no evidence of it.

Trump’s voter fraud claims really are baseless

There have been multiple investigations — by academics, journalists, and nonpartisan think tanks — into voter fraud. None found evidence of anything close to millions of people voting illegally.

Loyola Law School professor Justin Levitt studied voter impersonation, the type of fraud that strict voter ID laws (which Trump supports) aim to curtail. Levitt found 35 total credible accusations between 2000 and 2014, constituting a few hundred ballots at most. During this 15-year period, more than 800 million ballots were cast in national general elections and hundreds of millions more were cast in primary, municipal, special, and other elections.

A 2012 investigation by the News21 journalism project looked at all kinds of voter fraud nationwide, including voter impersonation, people voting twice, vote buying, absentee fraud, and voter intimidation. It confirmed that voter impersonation was extremely rare, with just 10 credible cases.

But the other types of fraud weren’t common either: In total, the project uncovered 2,068 alleged election fraud cases from 2000 through part of 2012, covering a time span when more than 620 million votes were cast in national general elections alone. That represents about 0.000003 alleged cases of fraud for every vote cast, and 344 fraud cases per national general election, in each of which between 80 million and 135 million people voted. The number of fraudulent votes was a drop in the bucket.

What’s more, not all — maybe not even half — of these alleged fraud cases were credible, News21 found: “Of reported election-fraud allegations in the database whose resolution could be determined, 46 percent resulted in acquittals, dropped charges or decisions not to bring charges.”

Trump and his team, in his defense, have cited a 2012 report from the Pew Center on the States as evidence for their claim. But the report didn’t even focus on voter fraud. Instead, it looked the technical aspects of voter registration systems, and how America could save money by upgrading how it registers voters.

As part of that, the Pew report found that more than 1.8 million registered voters were actually dead, while 2.75 million had registrations in more than one state. This is where Trump apparently got his “millions” figure.

But that doesn’t mean that even one of these registrations was used for illegal votes. America has a multi-step system for voting: You register, then vote. The report only shows that people registered and were never taken off the rolls. They didn’t even have to register for the latest election — some of them registered for the 2008 election, then died or moved, and states just didn’t take them off their rolls. So someone could have simply registered in Ohio in 2008, moved to Pennsylvania by 2012, and simply forgotten to notify Ohio’s elections system that he had moved — even though he never had any intention of voting in Ohio again.

And David Becker, who worked on the 2012 Pew report, unequivocally said that the 2012 report found “zero evidence of fraud.”

Watch: 6 ways your voting rights could be violated on Election Day