Here’s an interesting fact: When Obama leaves office, he’s no longer properly called President Obama. He’s back to being Senator Obama. That’s because whenever there’s an office that has only one holder at a time, only the current person is called by that title. The previous person defaults to being called the highest previous title ever held, so long as that title can belong to multiple persons. This is proper etiquette. It’s proper also to call them Mr. or Ms. or Mrs. So on Jan. 20, 2017, Obama becomes Senator Obama again.
I once got a letter read on-air by Brit Hume on this subject. I consulted Miss Manners. According to her, the POTUS and VPOTUS both revert to the highest title they had before serving as POTUS and VPOTUS.
With Trump, it would be “Mr. Trump.”
The living former Presidents would be Governor Carter, Ambassador Bush, Governor Clinton, Governor Bush, and Senator Obama. And calling ANY of them “Mr. Lastname” at any time is correct, both during and after their term as POTUS or VPOTUS.
It is NOT disrespectful of a President to call him “Mr. Lastname.”
It IS, however, idiotic, to call Abraham Lincoln “former President Abraham Lincoln.” Whatever happened to “the late Abraham Lincoln” or “the late President Lincoln”? (For those who haven’t been following the news.) Or, for those who HAVE been following the news, what’s wrong with “Abraham Lincoln”?