Inaugural Oath and Address
Article II, Section 1 of the Constitution specifies what the president-elect must say in order to take office:
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“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.”
At most of the early inaugurations, the president-elect delivered his inaugural address before taking the oath. Since 1865, every president, except President James Garfield in 1881, has taken the oath first and then delivered his address as president.