O.k., one instance, and one only. I said it would be a short answer.
Guess you didn't check the reference.
"Before he enters 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 the President of the United States, and will to the best of my ability, preserve, protect and defend the Constitution of the United States."
President Lincoln did that.
Walt
Yes indeed, he took the oath; in that instance he did abide by the Constitution. I acknowledged as much and don't understand what cause you have to quibble.