U.S. Democratic party Presidential candidates prepare to take part in a live National Public Radio debate in Des Moines, Iowa, December 4, 2007. The candidates are (L-R) Senator Hillary Clinton (D-NY), former Senator Mike Gravel (D-AK), Senator Barack Obama (D-IL), Senator Chris Dodd (D-CT), Senator Joseph Biden (D-DE) and Senator John Edwards (D-NC). REUTERS/Jason Reed (UNITED STATES)