That is the wording specified in the Constitution. In Article Two, Section One, Clause Eight, it says the president must take an oath and swear to preserve, protect, and defend the Constitution; the reason for it, undoubtedly, relates to the fact that the Constitution is our founding document and the basis for our laws.
To Preserve, Protect, and defend the constitution of the U.S.
...I will preserve, protect and defend the Constitution of the United States...
PROTECT, DEFEND and PRESERVE
President must take an oath to support the constitution before they can take office. The actual text isI 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."
PROTECT, DEFEND and PRESERVE
the president of the United States of America
"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."
He must "preserve, protect, and defend the Constitution of the United States."
all branches
preserve, protect, and defend the Constitution of the United States
He/She must preserve, protect and defend the Constitution of the United States
I, (say your name) 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."