This revised edition is a comprehensive resource for understanding public opinion polling in the US, including major and emerging theories and concepts; historical and current methodologies; political, journalistic, and corporate uses; landmark events and developments in the history of polling; and influential people and organizations. The encyclopedia also illuminates how public opinion polling has become important in shaping the trajectory of American society and the views that Americans have about themselves and their fellow citizens. Specific big-picture topics explored in this encyclopedia include how data mining of internet and social media usage trends has shaped modern political and business advertising campaigns; the impact of politically partisan media outlets on public opinion; and attitudes of various sectors of the American electorate about diverse topics including gun control, abortion, immigration, marijuana legalization, and the nation's two main political parties.