This is the first full-length book to examine how we interpret 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. Amid the widespread contemporary discussions of the challenge to modern democracy and the crisis of traditional forms of political representation, if offers a welcome emphasis on how party systems survive, and on how change, when it does occur, may be analyzed and understood.