Political parties exist at the centre of democratic politics, but where does power lie within them, and how is it exercised? The Political Party in Canada explores the inner workings of these complex organizations through an examination of the composition and roles of key party actors (members and activists, candidates, local associations, donors, central officials, and members of Parliament), as well as the interactions between them. Contemporary parties play a key role in recruiting and selecting candidates and leaders, waging election campaigns, and organizing legislatures. Drawing on a rich trove of data from the 2015 and 2019 federal elections, this comprehensive examination of Canadian party organizations explores a variety of party actors, from the local constituency office to party headquarters to Parliament Hill. The authors comb through interviews, surveys, financial and nomination reports, party websites and social media, and candidate and MP biographies, and examine the career trajectories of political operatives. Their analysis reveals the composition, functions, activities, and power-sharing relationships that characterize Canadian parties. It focuses not only on which groups are included in decision-making but also on what power and authority rest with each level of the parties’ respective structures. Basing its astute investigation on the themes of complexity, representation, and personalization, The Political Party in Canada provides important insights into a fundamental institution that makes modern democracy possible.