With the official business of the 57th inauguration out of the way, Washington began preparing Sunday for a day of revelry -- and for the challenges facing President Barack Obama over the next four years.

Satisfying the constitutional obligation to be sworn in on January 20, Obama and Vice President Joe Biden took quiet oaths the day before the public ceremony at the Capitol, which is expected to attract a crowd of up to 800,000 on the National Mall.

Obama will become only the 17th U.S. president to deliver a second inaugural address before leading the traditional parade up Pennsylvania Avenue to the White House.

Monday's events will be smaller than Obama's first inauguration in 2009, when nearly two million people witnessed the swearing-in of the country's first African-American president.

Less intensity this time reflects the reality of second-term presidencies, when the novelty and expectations of a new leader have been replaced with the familiarity and experiences of the first four years.

For Obama, that difference is even sharper.

His historic ascent to the White House in 2008 came with soaring public hopes and expectations for a new kind of governance that would close the vast partisan gulf developed in recent decades.

However, a list of challenges that included an inherited economic recession and repeated battles with congressional Republicans over budgets and spending only hardened the opposing positions in Washington.

Obama's signature achievements, including major reforms of the health care industry and Wall Street, became symbols of political division, with opponents constantly accusing him of hindering needed economic recovery.

A second-term Obama has vowed to press for an overhaul of the nation's immigration policies and new ways to boost the sputtering economy -- proposals that are bound to spark battles with his Republican rivals -- and oversee the implementation of Obamacare.