The oath is only 35 words, and honestly it is very easy to remember and quite famous.
That's not even true, though. Obama stumbled because Roberts screwed it up, and Obama knows the oath by heart. Roberts left off a "faithfully," and then inserted it at the end of the clause. Which confused Barry. Because John Roberts is not qualified to be the Chief Justice of the Supreme Court. He can't even read!
But at least he doesn't wear those stupid Gilbert and Sullivan fancy robes, we guess, like the last one.