January 21, 2009
The following is a statement from White House Counsel Greg Craig.
"We believe that the oath of office was administered effectively and that the President was sworn in appropriately yesterday. But the oath appears in the Constitution itself. And out of an abundance of caution, because there was one word out of sequence, Chief Justice Roberts administered the oath a second time."
Barack Obama, White House Press Release - Statement from White House Counsel Online by Gerhard Peters and John T. Woolley, The American Presidency Project https://www.presidency.ucsb.edu/node/323607