After John Roberts screwed up the administration of the oath at Obama's inauguration, some people suggested - some jokingly, some seriously - that Obama wasn't legitimately president. Well, now there's no doubt (discarding wacko conspiracy theories about how Obama was really born in Kenya or on Mars or something) because they went back and did it again:
The decision to repeat the oath was taken out of an abundance of caution, an official said.
But Mr Obama joked: "We decided it was so much fun...." before adding: "We're going to do it very slowly."
"We believe the oath of office was administered effectively and that the president was sworn in appropriately," said White House counsel Greg Craig.
"Out of the abundance of caution, because there was one word out of sequence, Chief Justice John Roberts will administer the oath a second time."
Two other presidents, Calvin Coolidge and Chester Arthur, have had to repeat the oath because of similar problems.