This is the cbs evening news with Norah Odonnell reporting tonight from the democratic debate in charleston, South Carolina. Odonnell good evening, and thank you so much for joining us toned as the seven candidates for the democratic president ial nomination will fight it out right here on this stage. This debate may be the most important, coming just four days before the South Carolina primary and one week before the 14state extravaganza known as super tuesday. Our latest cbs news poll shows joe biden with a slim lead here in South Carolina over the national frontrunner, Bernie Sanders. Billionaire tom steyer is polling third. Today, the candidates took turns walking through the debate hall, and the biggest question is whether anyone can slow down Bernie Sanders, who could be on track to take a significant lead in delegates. The others have already stepped up their attacks. In new ads, joe biden accuses sanders of trying to impede president obamas 2012 reelection. Pete buttigeig attac