The book explores the impact of uncertainty in the national campaign context on nonvoting in presidential and midterm House elections from 1920 through 2012. While previous studies have focused on individuals' motivations to vote and candidates' mobilization efforts, this book considers how uncertain national circumstances in the months before the election affect whether people vote or not. Uncertainty is defined as decision makers being unable to accurately predict future conditions, possible options, or final outcomes based on the current situation. Within the national campaign context, uncertainty arises from economic volatility, technological advances in mass communication, dramatic national events including wars, and changes in suffrage requirements. The book examines this uncertainty across four historical periods: the government expansion period (1920–1944), the post-war period (1946–1972), the government reassessment period (1974–1990), the internet technology period (1992–2012). The book considers the nature of politics during these periods with key occurrences including the economic swings of the Roaring 20s, the Great Depression, the post-World War II boom, and the Great Recession, voting rights for women, African-Americans, and young people, and the effects of radio, television, cable television, and the Internet on nonvoting. It concludes that the higher the degree of uncertainty in the national scene, the more likely eligible voters will go to the polls. Conversely, the lower the degree of uncertainty, as the national scene remains stable, the less likely eligible voters will participate. As one example, throughout all four historical periods, economic change decreases nonvoting, while economic stability increases nonvoting.