Many have assumed that he is a liar who deliberately and knowingly deceives the public. Others have contemplated whether he truly believes some of the nonsense that comes out of his mouth, thus challenging the notion that he is consciously lying. Of course, they are not mutually exclusive. Trump may be a true believer one day and a liar the next.
Some people will suggest the president actually believes in his own BS most of the time, and that he has come to live in his own warped version of reality. A man who decides what is true and what is false (i.e., “fake news”), regardless of the evidence. He has even come to question certain things that he had previously acknowledged as true (The Billy Bush recording). It seems, he's been a bullshit artist for so long that he has come to believe in much of his own bullshit. When one builds his entire career on fabrications and "Truthful Hyperbole" it is not surprising that they eventually come to believe the hype, especially when surrounded by an army of enablers and followers who would gladly bend and take a knee for him.