Chelsea Clinton sits with her father, former US President Bill Clinton, as they listen to US Democratic presidential candidate Senator Hillary Clinton (D-NY) speak at the National Building Museum in Washington June 7, 2008. Clinton endorsed presumptive Democratic presidential nominee Senator Barack Obama (D-IL) to be the Democratic U.S. presidential candidate on Saturday and suspended her own White House bid less than a week after the Illinois senator secured enough support to win the nomination. Clinton's endorsement of Obama in a speech at the National Building Museum marked the beginning of efforts to reunite the Democratic Party after a long and divisive campaign battle that ended on Tuesday when Obama won the support of enough delegates to clinch the nomination. REUTERS/Jason Reed (UNITED STATES) US PRESIDENTIAL ELECTION CAMPAIGN 2008 (USA)