Anderson Cooper 360

Soon: Democratic Candidates Take The Debate Stage; Sanders-Warren Feud Escalates Ahead Of CNN Iowa Debate; Will Warren Attack Sanders After Non-Aggression Pact Breaks Down?; Will Biden Go After Fellow Dems Or Only Focus On Trump?; How Will Klobuchar Try To Stand Out?; Drake University Student Sings National Anthem; Sanders Arrives At Debate Hall; DNC Chair Speaks Before Start Of Debate; Democratic Candidates Take The Debate Stage; Soon: Dems Hold Final Debate Before Iowa Caucuses via Knit