DPC Barack Obama (22 images)

Democratic presidential hopeful Sen. Barack Obama (D-Ill.) is joined by Oprah Winfrey before he addresses supporters at a rally at the Hy-Vee Conference Center in Des Moines, Iowa on December 8, 2007. Iowa voters head to the polls for a caucus on January 3, 2008. (UPI Photo/Brian Kersey)

Campaign buttons for Presidential candidate Sen. Barack Obama (D-IL) are displayed at the American Federation of State, County and Municipal Employees (AFSCME) 2007 National Leadership Conference in Washington on June 19, 2007. Over 2000 members of AFSCME gathered in Washington for the annual conference and to listen to five presidential candidates. (UPI Photo/Kevin Dietsch)

Sen. Barack Obama (D-IL) speaks at the International Association of Fire Fighters (IAFF) Bipartisan 2008 Presidential Forum, in Washington on March 14, 2007. Eleven official and possible presidential contenders will speak at the forum to gain the IAFF endorsement. Republican Rudolf Giuliani declined an invitation. (UPI Photo/Kevin Dietsch)

Democratic presidential candidate Sen. Barack Obama (D-IL) speaks to supporters during a campaign rally at the Fort Worth Convention Center in Fort Worth, Texas February 28, 2008. More than 11,000 people attended the event, his third of the day. Obama and Sen. Hillary Clinton (D-NY) are locked in a tight race headed into the Texas primary election on March 4, 2008. (UPI Photo/Ian Halperin)