Trump partially owned up to this during his early ascent as a national celebrity, when he and his ghostwriter, Tony Schwartz, published "The Art of the Deal" in 1987. Trump described repeated falsehoods, doublespeak and exaggerations as tools he used to get ahead in business and life, and labelled them "truthful hyperbole."
Schwartz, at least, feels bad about this. "'Truthful hyperbole' is a contradiction in terms," he told the New Yorker's Jane Mayer last year, in a mea culpa of sorts. "It's a way of saying, 'It's a lie, but who cares?' "
Schwartz also told Mayer that he regretted his collaboration with Trump and that if he were to write the book today he would title it, "The Sociopath."
Trump once sued me for libel, claiming that my 2005 biography of him, "TrumpNation," had damaged his reputation and business prospects. He lost the case in 2011, but during a deposition with my lawyers, Trump was revealed as having lied over the years more than 30 times about everything from the success of his business deals, and how much debt he had, to his actual ownership stakes in joint ventures, sales at his condominiums and even his speaking fees.
"Trump's falsehoods were unstrategic - needless, highly specific, easy to disprove," reporters David Fahrenthold and Robert O'Harrow Jr. wrote of the deposition in their 2016 Washington Post story headlined "Trump: A True Story."
During one exchange with my attorney during that deposition, Trump added another term to his lexicon of euphemisms for untruth: "mental projections."
After boasting about the profitability and success of his golf developments, Trump conceded in the deposition that those claims weren't based on anything other than his imagination; he had never undertaken a formal financial study of the projects' performances or prospects.
"No, I have never done an analysis," Trump said.
"Have you ever done a projection as to how much you will profit on these courses over time in light of the contributions that you're making in cash?" asked my lawyer.
"Yes, I've done mental projections."
"Mental projections?"
"Yes."
"These are projections that you've done in your head?"
"Yes."
During last year's presidential campaign, Trump lied repeatedly, asserting that President Barack Obama and former Secretary of State Hillary Clinton founded the Islamic State jihadist group; that "large-scale voter fraud" always happened on and before Election Day; that Ted Cruz's father was involved in the assassination of President John F. Kennedy; that there were 30 to 34 million illegal immigrants in the US; that he had always opposed the Iraq War, and so on.
Like Trump's public relations advisers in the 1980s, 1990s, and 2000s - and like Spicer and Conway today - Trump surrogates are forced to rationalize Trump's meanderings.
"In his mind, he's taking information and rendering an opinion," the developer Tom Barrack told CNN earlier this week, explaining how Trump came up with data points no one else had indicating that millions of people voted illegally in the presidential election.
Over the last week, Conway has tried to rebrand "alternative facts" as "alternative information" and "incomplete information." The latter two are unlikely to be the phrases that stick, however. Even so, Conway continues repackaging Trumpisms with brio, telling the Hollywood Reporter this week of her zeal for her role and the power Trump has invested in her. "If you see me on TV, it's because he wants me there," she said.
Spinning takes energy, however, and it requires unpeeling some moral glue to do it day after day - especially in the Trump era, when misdirection and lies are likely to be regular occurrences. For his part, Trump has done this for decades and it hasn't appeared to take much of a toll on him.
But the White House's machinations are likely to take a toll on Conway, Spicer and Trump's other advisers (as it did on some of their predecessors in decades past) if they decide to stay in the presidential arena for long. Proximity to Trump can be corrosive.
All of this is also likely to take a toll on a public that Trump has just settled in to serve for the next four years -- unless Congress, the business community and other institutions join average citizens in standing up for the idea that old-fashioned facts do matter.
- O'Brien is the executive editor of Bloomberg Gadfly and Bloomberg View. He has been an editor and writer for the New York Times, the Wall Street Journal, HuffPost and Talk magazine. His books include "TrumpNation: The Art of Being The Donald."