Barry Obama:
US Democratic presidential candidate Senator Barack Obama (D-IL) (top C) waits to hear US Commander in Iraq General David Petraeus (bottom) testify before the Senate Foreign Relations Committee on Capitol Hill in Washington April 8, 2008. REUTERS/Jonathan Ernst (UNITED STATES)
Democratic Presidential hopeful, and Senate Foreign Relations Committee member, Sen. Barack Obama, D-Ill., listens as Gen. David Petraeus and U.S. Ambassador to Iraq Ryan Crocker testify on Capitol Hill in Washington about the future course of the war in Iraq in this Sept. 11, 2007 file photo. When Petraeus delivers his assessment of the Iraq war April 8, the next commander in chief will weigh in as well. Republican Sen. John McCain will get a chance to argue that last year's U.S. troop buildup has been a success and withdrawal would be a mistake. Democratic Sens. Hillary Rodham Clinton and Obama will have an opportunity to ask why the United States is still fighting more than five years after the invasion. (AP Photo/Susan Walsh, File)
Democratic presidential hopeful Sen. Barack Obama, D-Ill., a member of the Senate Foreign Relations Committee, reaches for photographers on Capitol Hill in Washington, Tuesday, April 8, 2008, prior to the start of the committee's hearing on the status of the war in Iraq. (AP Photo/Alex Brandon)
Bill Clinton
Former U.S. President Bill Clinton, center, talks with U.S. Sen. Robert Menendez, D-N.J., left, while campaigning for his wife Democratic presidential hopeful Sen. Hillary Rodham Clinton, D-N.Y. at a rally in Barceloneta, Puerto Rico, Monday, April 7, 2008. At right is Romero Barcelo, former governor of Puerto Rico. The U.S. Caribbean territory will hold a Democratic primary on June 1 that could help decide the race for the nomination between Sen. Hillary Clinton and Sen. Barack Obama, even though Puerto Ricans cannot vote in the general presidential election. (AP Photo/Brennan Linsley)