DPC Barack Obama (22 images)

Democratic Presidential candidate U.S. Sen. Barack Obama speaks at the Service Employees International Union conference in Washington on September 17, 2007. (UPI Photo/Yuri Gripas)

U.S. Senator and Democratic Presidential candidate Barack Obama (D-IL) speaks at the AFL-CIO Building and Construction Trades Presidential Candidate Forum in Washington March 28, 2007. (UPI Photo/Yuri Gripas)

Supporters cheer for Democratic presidential candidate Sen. Barack Obama (D-IL) 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)

U.S. Democratic presidential candidates Senator Barack Obama (D-IL) and Senator Hillary Clinton (D-NY) share a hug and talk at the conclusion of the CNN/Los Angeles Times Democratic presidential debate in the Hollywood section of Los Angeles on January 31, 2008. (UPI Photo/Jim Ruymen)