This is a social history of political polarisation as it evolved in one city over three and a half decades before the Spanish Civil War. As such it is a book about the long-term origins of the War as seen 'from below'. More broadly it is an analysis of the evolution of political culture during the transition from elite to mass politics. The book focuses on the interplay between the three main forces that competed for political control: the conservative monarchist/Catholics, the democratic republicans, and the revolutionary trade movement. It is different from other Civil War studies, in trying to understand the relationship between organised political forces and the 'masses' they sought to reach. In doing so it reveals a rich canvas of participants and activities, from trade unions and strikes to female consumer riots.