Abstract
This introductory chapter sets the stage for the theoretical and empirical contributions included in this volume. It first justifies our adoption of the ‘ideational approach’ to defining populism. Then, it provides a first overview of a typology of party competition. This will be used in the country-specific chapters for the study of interaction dynamics between populist parties and their main non-populist counterparts, but also between populists competing with each other. The chapter moves to a brief description of the case studies (countries and parties) and also clarifies some of the geographical and political criteria used for their selection. The final part presents an outline of the book, which also includes some information about the structure of each country-specific chapter.