This book attempts to fill the gap in the understanding of how congressional leaders are chosen. It offers the first systematic analysis of party leadership elections in Congress since the 1970s, looking in particular at how election campaigns unfold and the factors driving lawmakers' vote choice when vacancies occur or challenges erupt against sitting leaders. This chapter begins with a brief review of the House's major elected party leadership positions. It then discusses the common wisdom about congressional leadership elections and the limits of early research on the topic. Next, it introduces a new theory of leadership selection and explain how candidates, campaigns, and political context contribute to the factors that shape legislators' vote choice for a leader. It then introduces the empirical data used in this study, describes the testing methodology, and outlines the chapters that follow.