If in fact it was The Trumpster (it does sound like him) that did the very poor impersonation of his supposed PR guy John Miller years back to boost his ego; the best thing for him to do is to admit it – take the lumps, come clean and march on.
If he continues to go the denial route that will put him in the same category as:
The true mark of a man or a women (hard to make the distinction sometimes) is their ability to be forthright and tell it like it is.
A liar usually has to tell 20 lies to get out of one. By the time they tell the 20th , they forgot what the first lie was.
EVERYONE in this world does foolish things sometime or another in their life that they may be ashamed of.
The initial impact my hurt but:
Fess up Donny and move on.