John King explains voting in early primary voting states

CNN’s John King explains how early primary voting in Iowa, New Hampshire and South Carolina works. Tune in at  7 p.m. ET, for CNN’s coverage of the Iowa caucuses: CNN anchors Wolf Blitzer, Anderson Cooper, Erin Burnett, Candy Crowley and John King will lead CNN’s election night coverage. The network will unveil several new technologies to break down the Iowa caucus process and results.