This panel analyzes the variety of ways in which territory, broadly understood, affects political parties. In particular, the papers analyze parties’ territorial organization, the electoral strength of regionalist parties, the tensions between national and regional MPs in statewide parties, and the relationship between statewide and regional parties in parliament. Therefore, the papers cover a number of arenas of party behavior: on the ground, within the party organization and within state institutions. The papers are both methodologically diverse and empirically rich. Wuhs deploys a historical-institutional approach to analyze the territorial organization and development of Germany’s CDU in the five states carved from the former East Germany. Massetti and Schakel test whether political decentralization undermines or strengthens regionalist parties’ electoral performance by employing a dataset of elections in 329 regions and 18 countries. Using data from a survey of parliamentarians and regional party manifestos, León-Alfonso, Alonso and Pérez-Nievas analyze the variation between national and regional MPs’ preferences regarding devolution in Spain’s main statewide parties, and the challenges it presents. Field, based on a dataset of legislator votes and elite interviews, analyzes the bargaining relationship between Spain’s statewide and regional parties during minority governments, drawing attention to the importance of the two-dimensional party system for understanding parliamentary alliances.