‘Ils Ne Passeront Pas!’: New Parties and Party System Nationalization in Europe (1946-2020)

This paper examines the impact of new parties on party system nationalization (PSN). While research on this topic is limited, this study challenges the prevailing notion that new parties consistently reduce the nationalization of party systems. Instead, it argues that the impact of new parties on PSN is a dynamic phenomenon that is contingent upon the nature of new parties and the manner in which extant parties respond to the emergence of these new challengers. First, the PSN should be negatively affected if the emergence of a new party corresponds to a challenger party, because these parties tend to attract concentrated electoral support, whereas new mainstream parties should actually increase it due to the nature of their electoral support. Secondly, extant parties are not indifferent to these new challengers. If extant parties increase their local manifestos as a result of the emergence of new parties, the PSN should be negatively affected because national politics become more local-centred. To test these hypotheses, the study analyses more than 300 elections from 1946 to 2020 in 20 European countries. The results partially confirm previous hypotheses. PSN reduces when new parties are challengers. Instead of changes in the local manifestos of extant parties affecting PSN, changes in the national manifestos do. This study adds to the existing comparative politics literature by providing new insights into the geographic nature of new parties' transformative capacity in advanced industrialized democracies.