I do not agree, although I will admit that defining “defining characteristic” is needed if we really wanted to do this right, even though I’m not really up for it. So, continuing in a casual way, I’d say his most defining characteristic is his lying.
A lot of liberals get upset about the wrong thing when he lies. His lying not really so pointed, it’s merely that he says whatever will make him look good and others look bad, and if what he says turns out to be true, fine; if it turns out to be false, fine. True or false is not the point, so it’s not like he is trying to tell a deliberate lie for some pointed purpose, like how most people think of lying, I’d imagine.