Mobilizing party activism: A field experiment with party members and sympathizers

Electoral mobilization and persuasion are often characterized as two-stage processes, where parties activate their core supporters, who then mobilize and persuade larger shares of the electorate. While there is a lot of research on the second stage of this process, the mobilization and persuasion of the wider electorate by party activists, there is little causally identified evidence on whether party elites can encourage campaign activism among party members and sympathizers. To address this question, we conducted a randomized field experiment in cooperation with the Swiss Social Democratic Party in the context of the 2015 cantonal elections in Ticino. The experiment consisted of the randomized administration of telephone calls to members and strong supporters of the party, while their self-reported campaign activism and attitudes towards the campaign were measured in a two-wave online panel survey. Against expectations, we record null effects on various measures of campaign activism, including on the mobilization of relatives, and friends. The results raise questions about omitted variable bias in observational studies of party activism that consistently report large positive effects of party contact on the campaign activism of members and sympathizers.