The most important element in every election is getting voters to the polls--these get-out-the-vote (GOTV) efforts make the difference between winning and losing office. With the first three editions of Get Out the Vote, Donald P. Green and Alan S. Gerber broke ground by introducing a new scientific approach to the challenge of voter mobilization and profoundly transformed how campaigns operate. Get Out the Vote has become the reference text for those who manage campaigns and study voter mobilization. In this expanded and updated edition, Green and Gerber incorporate data from a trove of recent studies that shed new light on the cost-effectiveness and efficiency of various campaign tactics, including door-to-door canvassing, e-mail, direct mail, and telephone calls. The new edition gives special attention to "relational organizing" through friend-to-friend communication and events. Available in time for the 2020 presidential campaign, this practical guide to voter mobilization will again be a must-read for consultants, candidates, and grassroots organizations.