The man is a habitual, congenital liar.

He lies even when it gives him no particular advantage or benefit. He lies when he knows it can be easily checked and shown to be false, or even when it is obvious he's lying on its face. He lies because he knows that it will add emphasis to his words or claims that will have a longer-lasting effect than the revelation later on that it is a lie.

He has mastered the art of the self-reinforcing lie. He knows the psychological boost his lie will temporarily add to his followers will outlast the eventual realization to everyone else that it IS a lie. His cult will revel in the "AHA! So there! Take that!" aspect of the lie, (his victims are always looking for someone to blame, and for painful and humiliating revenge on their enemies). They find the lie more pleasurable and reinforcing than the inevitable discovery that it is not true.

Besides, even if incontrovertible proof of the lie is demonstrated later on, it can always be dismissed with a "All politicians do that."

He lies because all businessmen lie, all advertisers and propagandists do, its why they never take responsibility for their lies in court, or whatever harm their products or claims do to consumers and investors, employees, creditors or the environment. They figure that even if the marks eventually realize its a lie, by the time they do they will have bought and paid for the con anyway. Evading consequences is always easier than asking permission.

There is no "truth in advertising" law, but they have managed to convince the rubes there is. They lie because they feel they are entitled to do so because they are better than the rest of us.