A Methodological Note Abstract Studies of new political parties often attempt to explain the latter's electoral success. Methodological problems linked to the notion of selection bias hamper, however, considerably the results of such studies. An empirical example studying the impact of rules regulating the access to ballots in national elections of 21 Western democracies illustrates this problem. Taking into account the formation process when studying the success of new parties allows, however, for a correction.
Similar solutions exist for other research designs employed to study the success of new parties.