Rare bumbling from two guys not known for it. The One stepped on the first line but it was the Chief who completely botched the next. Good thing Obama paused and nudged him to try again; god only knows how many lawsuits we would have seen from birth-certificate Truthers claiming he’s not really president because he never said the magic words.
Update: People are still insisting in the comments that Obama screwed up. Here’s the constitutional oath; follow Roberts on the second line: “I do solemnly swear that I will faithfully execute the office of President of the United States and will to best of my ability preserve, protect, and defend the Constitution of the United States.”