Take the whistleblower complaint that kick-started the Ukraine scandal. Trump has repeatedly said it’s inaccurate, which Tapper considers a “lie” given that an investigation and testimony have largely corroborated the whistleblower’s claims.

“He’s repeated that so many times that there’s obvious malice of forethought,” Tapper said of the president. “He’s obviously saying this in order to undermine a fact, in order to try to gaslight the country.”

Trump’s dishonesty in the White House has been thoroughly documented. Washington Post fact-checker Glenn Kessler and his team have tallied more than 13,000 false or misleading claims since taking office, while CNN’s Daniel Dale this week highlighted 45 false claims specifically about impeachment and Ukraine. The New York Times counted more than 1,700 conspiracy theories on Trump's Twitter feed.

But Tapper said he’s trying to go beyond the sheer volume of erroneous and misleading claims in a Sunday 9 p.m. special — “All The President’s Lies” — and address the impact on business, science, international relations and the national psyche. For instance, how might a false claim about trade talks with China affect global markets — and more broadly America’s credibility on the world stage?

“God forbid there should be some major international crisis where the United States president needs the people of this nation and the world to believe what he says about something,” said Tapper, asking, “What would the result be?”

Tapper, who hosts “The Lead” on weekdays and Sunday morning’s “State of the Union,” said part of the impetus for a special report was because there are “so many lies and falsehoods that we can’t even get to covering them all on any given day.”

The White House did not participate in the CNN project.

"CNN did ask us if we wanted to participate in some documentary, but would not tell us the topic or other participants, making it hard for us to adequately prepare," White House press secretary Stephanie Grisham told POLITICO.

A CNN spokesperson said the network informed the White House press office on Nov. 7 that Tapper was working on a special “about the president and his relationship with facts" and made additional attempts seeking their participation.

For the special, Tapper said he spoke to fact-checkers, like Kessler and Dale, along with historians, politicians, and scientists in producing what he considers “a nonpartisan analysis” of “the various lies the president has told and what the impact may be.”

Tapper doesn’t appear concerned that doing a prime-time special on the president’s “lies” might be perceived by some as partisan, especially as Trump and his allies routinely accuse the news media, and notably CNN, of siding with Democrats against his administration.

Tapper points out that he aired a segment on PolitiFact’s “Lie of the Year” when President Barack Obama was on the receiving end of that designation for saying if Americans like their health care plan, they "can keep it" under the Affordable Care Act. Now, if House Speaker Nancy Pelosi “were lying to this degree," he said, “we would be calling it out as well.”

But it’s not partisan, he insists, to put Trump in another category given that he “says more things that are demonstrably, empirically false on a daily basis than any other president before him in the modern era and more so than any major U.S. politician.”

“Facts are facts. The earth is not flat,” Tapper added. And the news media, he said, is supposed “to provide accurate information” and “sort through the spin — what really happened, and what is the truth, regardless of who’s asserting it.”

And yet facts may not always be enough to convince the public what really happened.

Nearly half of Americans recently polled believe “it’s difficult to know whether the information they encounter is true,” the Times noted this week. One can find dramatically different framing of events on television in prime time and on social media.

The president’s desire for Ukraine to launch investigations stemmed largely from conspiracy theories, like the debunked claim that Ukraine, not Russia, interfered in the 2016 election, which Trump again pushed Friday in an interview on “Fox & Friends.”

Also, there’s also no evidence former Vice President Joe Biden urged the dismissal of a Ukrainian prosecutor to protect his son Hunter’s business interests.

Tapper said some of Trump’s defenders are claiming he “never requested a foreign government to look into the Bidens.”

“That’s just a lie. That’s just false,” said Tapper, citing the rough transcript of Trump’s infamous July 25 call with Ukraine’s president. (Tapper tweeted Friday it is “not in dispute” that Trump sought the investigations from Ukraine into the Bidens and the 2016 election).

“There is an attempt among some individuals to create an alternate reality where the president did not say what he clearly said,” Tapper said. “And we just have to state what the facts are.”