This article examines why and how political leaders emerge and, once in charge, what determines their success or failure. To explore these questions, I present a theory of political leadership that takes into account both the structural and the behavioral aspects of the concept. I argue that the emergence and the impact of leadership represent two different analytical steps. A leader emerges if there is a supply of, and demand for, leadership. While the supply depends on a leader's expected benefits, the demand is determined by the followers’ status quo costs. The second step concerns a leader's impact, which results from the strategies deployed by the leader. While a leader's capacity to employ strategies is determined by the power resources at its disposal, the intensity of strategies needed to influence outcomes depends on the heterogeneity of preferences and on the adaptability of the institutional setting. The theory is applied in the context of the current eurozone crisis by analyzing Germany's role in shaping the European Fiscal Compact.