Traditionally political donating behavior has been explained using socio-demographic and socialization-based models. The dramatic increase in the number of donors between 2000 and 2008 and the virtual elimination of structural barriers that limited donating to a select few suggest that this explanation is no longer adequate. What differentiates individuals who donate from those who do not? To answer this question I expand the traditional funnel of causality to develop a theoretical model that integrates biological, psychological, political behavior, and rational choice approaches. Using five samples, three nationally representative and two population-based surveys collected in 1990 and 2008, I investigate each level of the new funnel of causality using empirical models. I find that the best predictors of political donating are personality and attitudes, with a small role of context in the form of direct contact from parties. This new model explains more of the variance in political donating than the traditional model, and represents the most theoretically and empirically complete models in the literature.