Every Presidential oath of office ( Franklin D. Roosevelt Donald J. Trump)

United States Constitution, Article II, Section 1, Clause 8: Before the President 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 to preserve, protect and defend the Constitution of the United 4 March 1933; Governor Franklin D. Ro