“…This article contributes to the literature on parties empirically through this new dataset, and theoretically, by placing emphasis on party organization as a key explanatory variable. For quite some time studies of parties and party systems have neglected the role of party organization, 2 but recent studies suggest that it might be an important dimension to understand a variety of political outcomes such as electoral success (Janda and Colman, 1998;Tavits, 2011;Greene and Haber, 2015;Ishiyama, 2001), changes in party policy position (Schumacher, de Vries and Vis, 2013) and the number of parties in a party system (Chhibber and Suryanarayan, 2014). 3 Within this recent research agenda, this article is the first to investigate how party organization affects the territorial nature of parties' electoral support.…”