CNN's Gloria Borger this week talked with multiple former business associates of President Donald Trump, who all explained why he has a habit of lying about everything he does.
Borger starts off by talking to former Trump Organization executive Barbara Res, who reveals that Trump planted a fake story about Princess Diana looking for an apartment in Trump Tower back in the 1980s as a way to hype up sales for the building.
"That didn't happen?" Borger asked Res.
"No," Res replied. "But it made the papers."
While this kind of lie might seem harmless, Trump's constant stream of untruths often ended up coming back to haunt him and those who trusted him, as was the case of the failed Trump Taj Mahal Casino in Atlantic City.
Architect Alan Lapidus, who worked for Trump in the past, told Borger that the New Jersey Casino Control Commission actually shut down one third of Trump Taj Mahal's slot machines on its opening day because they didn't work properly.
"To shut down a third of the slots on opening day was both humiliating and financially disastrous," he said.
Undeterred by this, Trump found a way to lie to the public about why so many slot machines had to be taken offline -- and he told TV host Larry King that the machines were shut down because they got overheated from too many people using them.
"Truly, he would just lie about everything," said former Trump Plaza Casino manager Jack O'Donnell.
Watch the video below.