Democratic presidential candidates have completed a debate with an unusual format. The questions they received came through videos prepared by people worldwide and submitted to the online video Web site "YouTube." The Monday evening debate in Charleston, South Carolina, was broadcast on the CNN cable news channel. People submitted questions about the candidates' thoughts on the situation in Sudan's Darfur region, and whether they thought U.S. troops should be sent. Senator Joseph Biden said he would send U.S. troops to stop the violence in Darfur. New Mexico Governor Bill Richardson said he favored establishing a no-fly zone and increasing the number of United Nations peacekeepers. Senator Hillary Clinton said she would not send U.S. troops to Darfur, but would move more quickly on sanctions and diplomacy. Other questioners inquired about how the candidates would handle national disasters, and whether they support same-sex marriage. The Republican candidates will take questions in the same format when their debate is held in September.