In this dissertation I develop a theoretical framework for understanding why citizens do or do not engage in politics and civic society and how organizations, through their appeals, impact these decisions. Specifically, I broaden the 'calculus of voting' and borrow from John Zaller's (1992) theory of how people answer survey questions. Using this framework, I generate a number of hypotheses about what types of people should participate when solicited, as well as which appeals work best in particular contexts and for whom. In the three empirical chapters, I test these hypotheses using survey and field experiments. I conclude with recommendations for future scholarship in this area, noting its practical importance for increasing participation rates generally and decreasing the participatory gap, which are two ailments of American Democracy today.