This volume offers an overview of party politics in Mexico, with a special focus on the 1997 mid-term congressional elections. In Mexico the three main political parties have led the advances towards democratic governability. Chapters on the PRI (Partido Revolucionario Institucional), the PAN (Partido Accion Nacional) and PRD (Partido de la Revolucion Democratica) examine the responses of these three leading parties to changing electoral challenges. As competition for the vote increased, these parties have been forced to adapt and to introduce changes in their organization. These changes have had wider implications for the development of the party system. In consequence, this volume is more than the study of leading competing parties in Mexico. It also analyses the behaviour of the Mexican electorate and the changing institutional setting that underpins both the nature of political parties and the patterns of competition and co-operation.