I want to say “First Gentleman”. What would the media call him?
They’d go with “First Gentleman” except for the media who still don’t like him. They’d probably use something like “First Adulterer.”
Would First Gentleman trump Mr. President?
First Former President?
From my understanding of etiquette, you use his last highest office other than President.
Only the current President should go by “Mr. President” or “President[Name]”.
Bubba. He has always been, and will always remain, Bubba to me.
As far as the media are concerned, they seem to be going with “Former President, Bill Clinton.” “Bubba” is shorter.
There is a ceremonial order of precedence in the United States, which establishes (basically) who goes in to dinner first, and who sits where. (It has nothing to do with succession to the office of President, or who can give orders to who.)
Unsurprisingly, it’s headed by the President of the United States. And, in general, husbands and wives take their precedence from their spouses, so the first lady or first gentlemen has the same precedence as the President. So, first lady/first gentleman outranks former president. (Former presidents come a bit down the list, after the Chief Justice of the United States.) If Hillary is elected President, Bill will go up in the order of precedence, and take the status appropriate to the spouse of the President rather than the status of former President.
But . . .
The position of first lady isn’t associated with any particular form of address. You address the first lady as “Mrs Obama” (or “Ma’am”).
Although it has no official standing (and isn’t, in fact, followed by the State Department) there’s a social convention in the US that former holders of certain offices, including the presidency, continue to be addressed with the form of address used for the holder of the office. So Bill Clinton is often referred to as “President Clinton” and I dare say from time to time people address him as “Mr President”. It’s not technically correct, but it’s common. And I doubt that this will stop if he become first gentleman.
First Lad
No, etiquette goes with the last, highest rank. “Mr President Bush” and “Mr President Clinton.” It’s only polite, and they require you to work out the chronology. You’ve never heard Dubya called “Mr Governor,” have you?
Since there is no precedent in the matter, this is probably better suited to IMHO.
Colibri
General Questions Moderator
Clinton himself has suggested “First Laddie.”
My bet is Former President is going to be used a lot but to be frank I don’t see Hillery having him around that much except for the obligatory “happy family” photo ops. He’s worth too much speaking and (pardon the expression) running around on his own.
FGOTUS just doesn’t have the right ring to it.
So this would work better.
“Co-President”, just like it was before. 
First Mister. Or First Husband.
As far as Mr. President, maybe face-to-face, but in third person it isn’t unique.
Eh, screw it, you’re right. Bubba.
If you had titles like we do, you could make him a Duke.
When Margaret Thatcher was Prime Minister, her husband kept a pretty low profile and was just plain Mister.
The Duke of Earl? Has a certain ring to it.
How about First Bubba? After all, there are other Bubbas out there.
First Dude?
I love Miss Manners dearly, but she’s simply out of date on that one. The exception for Presidents has not been generally observed for generations now. Bubba will either continue to be President, or former President, Bill Clinton when referred to as himself. When referred to as the spouse of President Clinton, the obvious title is First Gentleman. I would expect that term to get used by anyone who wants us to get used to it for future use by future male spouses of Presidents.