US Democratic presidential candidate Senator Barack Obama (D-IL), (L) smiles as he is joined onstage with Senator Edward Kennedy (D-MA), (R) and Caroline Kennedy during a rally at American University in Washington, where Kennedy endorsed Obama's candidacy, January 28, 2008. REUTERS/Mike Theiler
US Democratic presidential candidate Senator Barack Obama (D-IL) (L) hugs Senator Edward Kennedy (D-MA) during a rally at American University in Washington, where Kennedy endorsed Obama's candidacy, January 28, 2008. (Mike Theiler/Reuters)
Democratic presidential hopeful Sen. Barack Obama, D-Ill., takes in the applause of the crowd and from left, Sen. Edward Kennedy, D-Mass., Caroline Kennedy, daughter of the late president John F. Kennedy, and Rep. Patrick Kennedy, D-R.I., during a rally on the campus of American University in Washington, Monday, Jan. 28, 2008. Obama was endorsed by the three Kennedys Monday. (AP Photo/Charles Rex Arbogast)
Democratic presidential hopeful Sen. Barack Obama, D-Ill., stands with Sen. Ted Kennedy, D-Mass., right, Rep. Patrick Kennedy, D-R.I., left, and Caroline Kennedy, daughter of the late president John F. Kennedy, second from right, during a rally for Obama at American University on Monday, Jan. 28, 2008, in Washington. (AP Photo/Evan Vucci)
Democratic presidential hopeful Sen. Barack Obama, D-Ill., addresses an outside overflow crowd on the campus of American University in Washington, Monday, Jan. 28, 2008, after he was endorsed by Sen. Edward Kennedy, D-Mass., and other members of the prominent Democratic party family. (AP Photo/Charles Rex Arbogast)
Democratic presidential hopeful Sen. Barack Obama, D-Ill., works the crowd with Sen. Edward Kennedy, D-Mass., at a rally on the campus of American University in Washington, Monday, Jan. 28, 2008, after he was endorsed by Sen. Kennedy, and Caroline Kennedy, the daughter of the late president John Kennedy.
(AP Photo/Charles Rex Arbogast)
Supporters of Democratic presidential hopeful Sen. Barack Obama, D-Ill., cheers during a rally on the campus of American University in Washington, Monday, Jan. 28, 2008. Obama was endorsed during the rally Monday by Sen. Edward Kennedy, D-Mass., and other members of his prominent Democratic Party family.
(AP Photo/Charles Rex Arbogast)
Democratic presidential hopeful Sen. Barack Obama, D-Ill., waves to supporters with Caroline Kennedy, daughter of the late president John F. Kennedy, after she endorsed him during a rally at American University in Washington, Monday, Jan. 28, 2008. (AP Photo/Evan Vucci)
Democratic presidential hopeful Sen. Barack Obama, D-Ill., sits with Caroline Kennedy, daughter of late president John F. Kennedy, right, during a rally for Obama at American University on Monday, Jan. 28, 2008 in Washington. Caroline and others in the Democratic Party's prominent political family, endorsed Obama for president on Monday, with Sen. Edward M. Kennedy calling him a 'man with extraordinary gifts of leadership and character,' a worthy heir to his assassinated brother.
(AP Photo/Evan Vucci)