In fact, most of the suggestions here, while excellent, are descriptors.
Descriptors rarely stick to a person, however accurate they may be. A nickname, on the other hand, is a term you use when you casually address someone directly, and that’s what helps them stick to a person:
“Hey, Chedderhead, stop whining about the delegate rules!”
Etc.
Good point.
Maybe, just plain “Loser”? It’s exactly what he called people. Practice saying it, with the accent and the volume.
After thinking about the thread title, what about, “The Don-key”?
Donkey Don? I kinda like that. 
Charles P. Pierce, columnist at Esquire, routinely refers to him as He, Trump and a vulgar talking yam. Example:
Trumplestiltskin is one of my favorites, but it didn’t take off. I thought of it myself in the context that I came up with it independently of the people who came up with it first, whoever they may be.
I googled it and found this masterpiece. TRUMPLESTILTSKIN - THE AMERICAN DREAM - YouTube
Mr. Cats
I was hoping something along the lines of “Durr Furor”, “Derp Furor”, or maybe “Hair Furor” would catch on. But apparently it was not to be.
I love Hair Furor! For me that’s the best one so far.
Donald Tromp. 
The Ham Sandwich and Orange Drink Combo
Hell Toupée.
He could take a stand against it from on high, but instead just insists that he’s not calling for violence against folks who aren’t hurting anyone; he’s, uh, noting that the crowd sure seems worked up, is all. Also, he really wants you to check out his hands. And if you bring a disputed claim to his attention, he shrugs it off, for what is truth?
So . . . Pontius Trump.
Since the first word that Donald brings to mind is duck, I’m going to try Donald Quack.
We could nickname him for the tactic he’s been known to advocate.
“Boycott Trump”
Has a ring to it, don’t you think?
He is Hitlery’s Enabler – only he can lose to her.
Donald Dunk Trump
The Drumpf-ah Loon-pah…?
Drumpf-ah! Drumpf-ah! Drumpf-ity Doo!
I’ve got Another riddle for You!
Drumpf-ah! Drumpf-ah! Drumpf-ity Dee!
If you are wise you’ll listen to me…
What do you get with a partisan hack?
Orange toupees? Bibles shoved up the back?
Who benefits from electing a Schmuck!?
Whores… always chase… the… buck…
(Whores always chase the biggest buck.)
(…he really is a Stupid Duck…)
Drumpf-ah! Drumpf-ah! Drumpf-ity Dah!
If you’re not greedy, you will go far!
You can live in happiness too…
Just don’t… listen to… Drumpf-ity… POO!!!
I heard someone call him Drumpelstilskin which made me LOL.
Not since 1987 anyway, when Ed Koch called him “greedy, greedy, greedy” and “piggy, piggy, piggy.”
So I agree with you. “Piggy” he was, and “Piggy” he shall be.
cough 