This unique and important new book looks at how we interpret the evidence of change and stability in modern parties and party systems. Focusing primarily on processes of political adaptation and control, it also concerns how parties and party systems generate their own momentum and `freeze' themselves into place. Amidst the widespread contemporary discussion of the challenge to modern democracy and the crisis of traditional forms of political representation, it offers a welcome emphasis on how party systems survive, and on how change, when it does occur, may be analysed and understood. The first part of the book deals with questions of persistence and change, and with the vulnerability and endurance of traditional parties. In the second part, attention shifts to the question of party organization, and to the ways in which the established parties are increasingly coming to invade the state, finding there a new source of privilege and a new means of ensuring their own survival. The third part of the book focuses on structures of competition in Western party systems, as well as on the problems associated with the consolidation of the new party systems in post-communist Europe. This is the first book to be entirely devoted to the question of party and party system change, and offers and essential guide to the understanding of this crucial theme.