‘He’s deteriorated’: Art of the Deal ghostwriter says Donald Trump is cracking under pressure as president

President Donald Trump is showing up at the Oval Office later and later each day. However, Tony Schwartz, who worked with Trump on The Art of the Deal said that he's seen a deterioration of the president over the years.

"He doesn't think as well as he once did," Schwartz told CNN's Alisyn Camerota Tuesday. In the past, . "He has clearly deteriorated."

The host wondered if in the past Trump repeated the same stories over and over again as biographer Michael Wolff is alleging.

"Well, Donald Trump has only told one story throughout his life and that's been 'I'm the greatest.' 'I'm the best.' Now that's advanced to 'I'm a stable genius,' but it's always been the same story," he said.

Schwartz said that he went back to look at interviews from previous years and compared them with recent interviews and that the decline is obvious. However, when Schwartz worked with Trump on their book, he was also watching a lot of television. The difference is that he was also working at the same time. Now, Trump is spending the majority of his time focusing on how he appears in the media and not coming into the office until after 11 a.m.

But when it comes to Trump's mental instability, Schwartz warns that Trump has always been mentally unstable.

"This whole phrase 'mental instability' is such a tough one," he said. "Did I think he was a deeply narcissistic guy? Yes... Do I think he was mentally unstable then? Yes, I do. In other words, do I think that if he was subjected to intense stress, do I think he would have behaved in ways that are scary? I do think that. At that time, it simply wasn't the case."

But now that Trump is the president and the pressure is on, Schwartz thinks it's destabilizing him.

When it comes to laziness, Trump has never been a lazy person. So, Schwartz is seeing him falter in the face of that pressure.

"He's either lazy or incapable of working," Schwartz said.

Watch the full interview below: