In a small and short ceremony at the White House, he will recite the constitutionally mandated oath for the third of four expected times during his time in office.
When Obama first took the oath on Jan. 20 four years ago, he and Chief Justice John Roberts tripped up over the wording, raising concerns about whether the constitutional requirements were fulfilled to the letter of the law. Roberts went to the White House the next day and administered it again in full.
This time, Obama will recite it twice on purpose. Sunday's official swearing-in, conducted again by Roberts, will be the 57th inauguration of a president in American history.
The short Sunday ceremony will be held because the constitutionally mandated inauguration date of Jan. 20 falls on a Sunday, so Obama will take the oath a fourth and final time on Monday before hundreds of thousands of observers on the National Mall. The Monday ceremonies will include the president's inaugural address, a luncheon with the president and members of Congress and the traditional inaugural parade and balls.