This study evaluates the validity and causal weight of competing mechanisms that purport to explain a single set of choices (and a critical turning point) within a contentious episode: the decision to participate in the Orange Revolution protests in Ukraine in November 2004. These protests were characterized by extraordinarily high levels of participation, despite freezing temperatures and the threat of violence. Using evidence from public-opinion surveys and eyewitness accounts, the study shows how causal processes unfolded and accumulated at several levels (structural, conjunctural, and endogenous). Overall, participation represented more of a short-term fluctuation than a general shift in societal values and behaviors, was fueled more by a long train of abuses than by suddenly imposed grievances, and was aided by a robust form of electoral campaigning. Events functioned as occasions for crafting together a diverse coalition of participants motivated by a variety of concerns--national, economic, and civic.