His wife, kids, old friends…? Or they do as well?
Canadians.
No one HAS to call him anything particular. And any law that said we did would violate the First Amendment.
Right, there is no law… but whom of his daily associates would not be calling him Mr. President ?
Anyone. It depends on the president. Most if not all presidents bring a certain amount of cronies along that they have known for a while. It wouldn’t surprise me if there are always a certain number of people who call the president by his first name behind closed doors. Why wouldn’t there be?
I agree… just checking on who would call him Donny
Me.
Since I doubt anyone here can give a factual answer, my speculation is that Melania and some others will call him Donald, but not Donny.
So, not snookems?
No. I can categorically state that Melania does not call him snookems.
Protocol dictates that foreign diplomats address him as “Your Excellency” as opposed to “Mr President”.
Miss Manners told the story that at one major gala given by JFK, people in the receiving line would call him “Jack”, in an attempt to show that they were “in” with the President.
Then the Attorney General came up and said “Good evening, Mr President.”
Miss Manners commented that it was an excellent example of how formality can be used to show one’s own social and political status.
I’m sure Ivanka, and possibly Jared, call him “Dad.”
Nitpick: “who … would … be calling … him”. It’s subjective case. The hint is that the clause already has an object, “him.”
I agree… saw it afterwards and was too lazy to change.
Look, if I was President, I confess that I’d be milking it. My wife would never come around, but heck, I would have someone would train my dog to address me that way: “Rood rorning, Rister Resident!”
I wouldn’t, even if I had to.
Given who JFK’s attorney general was, if this is a true story, it’s particularly amusing. 
From what I’ve heard, he is milking it. Supposedly there’s a button on his desk. When he presses it, a butler appears with a Coke.
I’m wondering what Robot Chicken will do with Trump. If they have a chance to get anything done for Season 9, depending on their lead times.