This is the oath of office:
“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 what the Chief Justice said:
I do solemnly swear that I will execute the office of President to the United States faithfully, and will to the best of my ability, preserve, protect and defend the Constitution of the United States.”
How hard is it to read this out to the President? Did he f*ck it up on purpose? Was it just something he did by accident? Obama was thrown a bit and at first it seemed like he was waiting for the CJ to say it right, but thank god it is only a couple of phrases and he is the President of the USA now!
Postscript: Roberts thought he was capable of memorizing the lines and screwed up. He later apologized to the President. No harm, no foul.