He says he opposed the Iraq war from the start. He didn't.
Never in modern presidential politics has a major candidate made false statements as routinely as Trump has. Over and over, independent researchers have examined what the Republican nominee says and concluded it was not the truth — but "pants on fire" (PolitiFact) or "four Pinocchios" (Washington Post Fact Checker).
Trump's candidacy was premised on upending a dishonest establishment that has rigged American political and economic life, so many of his loyalists are willing to overlook his lies, as long as he rankles the powerful, said Republican strategist Rob Stutzman.
"It gives him not only license, but incentive to spin fantasy, because no one expects him to tell the truth," said Stutzman, who worked against Trump during the primaries. "They believe they're getting lied to constantly, so if their hero tells lies in order to strike back, they don't care."
Still, Trump's pattern of saying things that are provably false has no doubt contributed to his high unfavorable ratings. It also has forced journalists to grapple with how aggressive they should be in correcting candidates' inaccurate statements, particularly in the presidential debates that start Monday.
At a time of deep public mistrust of the news media, the arbitration of statements of fact, long seen as one of reporters' most basic duties, runs the risk of being perceived as partisan bias.
But so does the shirking of that role. Fox News anchor Chris Wallace, one of the debate moderators, has faced a storm of criticism for telling CNN: "It's not my job to be a truth squad."
After a Sept. 7 town hall on NBC, critics skewered moderator Matt Lauer for failing to correct Trump's false statement that he opposed the U.S.-led invasion of Iraq. CBS correspondent Lesley Stahl drew milder reprimands for letting Trump repeat the same lie twice in a July interview on "60 Minutes," responding "yeah" both times with no correction.
Trump's Democratic rival faces integrity questions of her own. A new Wall Street Journal-NBC News poll found that 41% of voters saw Trump as better than Clinton at being honest and straightforward; just 31% thought that Clinton would be better than Trump in that area.
Republicans have used Clinton's use of a private email server when she was secretary of State to cast doubt on her honesty, saying she has been untrustworthy for decades. Her efforts to fight back were damaged when FBI Director James B. Comey said in early July that she had been "extremely careless" in her handling of emails that officials said should have been considered classified.
Nonetheless, the scope of Trump's falsehoods is unprecedented, and he is dogged in refusing to stop saying things once they are proved untrue.
BuzzFeed unearthed an audio recording showing that Trump backed the Iraq invasion and a 2011 video in which he called for swift military action against Moammar Kadafi, then the leader of Libya. In the months since those disclosures, Trump has lied dozens of times on both issues, saying he opposed the use of force in Iraq and Libya.
Trump campaign spokesmen Hope Hicks and Jason Miller did not respond to an email requesting comment on Trump's history of falsehoods.
Thomas E. Mann, a resident scholar at UC Berkeley's Institute of Governmental Studies, said Trump appears to recognize that a faction of the Republican Party has lost respect for facts, evidence and science — presuming, for example, that anything negative said about Obama is probably true.
Moreover, he said, the New York business mogul once thrived as a reality television star playing himself on "The Apprentice," and in that realm there's "no need to have any touch with genuine reality — it's all as he defines it."
"He's a salesman," Mann said. "He's a con man. He's hustled people out of money that they're owed. He's lived off tax shelters. He's always looking for a scheme and a con, and in that sphere, you just fall into telling lies as a matter of course."
In "Trump: The Art of the Deal," his 1987 best-seller, Trump said "a little hyperbole never hurts."
"People believe that something is the biggest and the greatest and the most spectacular. I call it truthful hyperbole. It's an innocent form of exaggeration — and a very effective form of promotion," he said.
Trump's coauthor, Tony Schwartz, put it less benignly in a July interview with the New Yorker. "He lied strategically," Schwartz recalled. "He had a complete lack of conscience about it."
"As we noted when we awarded Trump our 2015 Lie of the Year award for his portfolio of misstatements, no other politician has as many statements rated so far down the dial," PolitiFact writer Lauren Carroll reported in June. "It's unlike anything we've ever seen."
At a recent Trump rally in downtown Miami, supporters vouched for his trustworthiness.
"I think he has been very straightforward, whether people like it or not," said Rosario Rodriguez-Ruiz, 42, a Republican real estate broker and accountant.
Some in the audience conceded that Trump might have cut corners in business, but said they were more troubled by what they called Clinton's dishonesty about her email and the deadly 2012 raid on the U.S. diplomatic outpost in Benghazi, Libya. Miguel Pita, 56, said Trump had to "bend the rules" to avoid taxes. "I look at it as a 'Catch Me If You Can' type of deal," he said.
Suzanne Roberts, 61, a retired Miami finance professor, said Clinton was "capable of spreading heinous rumors about anything, anyone, at any time." As Elton John's "Funeral for a Friend" blasted through the concert hall's loudspeakers, she said Trump was correct to argue for five years that Obama was born outside the United States.
"He was born on a naval base in Mombasa, Kenya — that's what I think," Roberts said. "I've done some research."
A few days earlier, Trump spoke at a black church in Flint, Mich. When he started to criticize Clinton, the pastor interrupted and asked him not to give a political speech.
"The audience was saying, 'Let him speak, let him speak,'" Trump later told Fox News.
"That isn't true," reported National Public Radio correspondent Scott Detrow, an eyewitness. "In fact, several audience members began to heckle Trump, asking pointed questions about whether he racially discriminated against black tenants as a landlord."
When Trump released his child-care plan on Sept. 13, he said Clinton didn't have one. She did. He has often described himself as popular among African Americans; the latest Wall Street Journal-NBC News poll found 7% of black voters support him.
Trump also depicts crime as rising and out of control in America's inner cities despite years of falling crime rates. He has said that black people kill 81% of white homicide victims, when in fact whites kill 82% of white homicide victims, according to PolitiFact.
Marty Kaplan, a professor of entertainment, media and society at USC's Annenberg School for Communication and Journalism, has two theories on Trump's falsehoods.
Perhaps he's just putting on an act, like P.T. Barnum — a "marketer, con, snake-oil salesman who knows better, knows how to get the rubes into the tent." Or maybe, Kaplan suggested, Trump is just "completely unconstrained by logic, rules, tradition, truth, law."
"I'm confused," he said, "whether the whole fact-free zone that he's in is a strategic calculation or a kind of psychosis."