Well, according to the Constitution, Article II states: “Before he enter on the Execution of his Office, he shall take the following Oath or Affirmation:—‘I do solemnly swear (or affirm) that I will faithfully execute the Office of President of the United States, and will to the best of my Ability, preserve, protect and defend the Constitution of the United States.’”
Notice the lack of any name at all. So, it is simply a tradition to use any name at all, so on that point, Obama could be correct.
Politico did a story on it.
So, it is not a tradition to use all three names, it really is up to the person, however it seems using the name at all is the tradition that he could be referring to.
I may have jumped the gun by saying only recently they started doing this, but I knew that it was not always the case, but the last few had done it, but you get the idea regardless.
