More than 2.5 million votes have already been cast in Georgia's Senate runoff election. The rest of the state's voters will head to the polls on January 5. Only one of the two Republican incumbents needs to win for the party to maintain its majority in the Senate. If both Democratic challengers win, there will be a 50-50 split in the chamber, with the deciding vote going to incoming Vice President Kamala Harris. J. Miles Coleman, an associate editor for Sabato's Crystal Ball at the University of Virginia Center for Politics, discusses the tactics being used by the candidates less than a week before election day.