Democratic Debate (14 images)

Barak Obama signs a program book for a member of the audience after his debate with Hillary Clinton in the Kimmel Theater at the National Constitution Center in Philadelphia on April 16, 2008. (UPI Photo/John Anderson)

Democratic candidates Hillary Clinton and Barak Obama prepare for the beginning of their debate in front of a huge banner reading "We The People" in the Kimmel Theater at the National Constitution Center in Philadelphia on April 16, 2008. (UPI Photo/John Anderson)

Sen. Barack Obama (D-IL) (L) and Sen. Hillary Clinton (D-NY) (2nd R) greet ABC monitors Charles Gibson (2nd L) and George Stephanopoulos as they arrive at the National Constitution Center for their debate April 16, 2008. (UPI Photo/John Anderson)

Sen. Barack Obama (D-IL) (R) and Sen. Hillary Clinton (D-NY) greet the audience at the National Constitution Center before their debate in Philadelphia on April 16, 2008. (UPI Photo/John Anderson)