This is how it is:
"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."
This is how the guy swearing him in said it:
"I do solemnly swear (or affirm) that I will execute the office of President of the United States faithfully, and will to the best of my ability, preserve, protect and defend the Constitution of the United States."
-- Obama knew the oath from memory, that is why he looked like he didn't know.