Diffusion Processes and Discussion Networks: An Analysis of the Propensity to Vote for the 5 Star Movement in the 2013 Italian Election

The article aims to analyze the development of the propensity to vote for a new populist party, Movimento 5 Stelle (the 5 Star Movement, M5S), during the campaign for the 2013 Italian general election. The party, headed by a former comedian, Beppe Grillo, gained 25% of valid votes in the election, thus becoming the largest party in the Italian political landscape. Using rolling cross-sectional, pre-election data from the Italian National Election Study (ITANES), we show that the propensity to vote for the M5S is boosted by voters’ exposure to discussions on political matters with discussants from non-cohesive social groups (especially acquaintances). We also show that, together with the spread of support for this party, this effect increases during the campaign.