Replication Data for Betting on the Underdog The Influence of Social Networks on Vote Choice

What makes people vote for an underdog? The common expectation is that people avoid wasting their vote on a party with a small probability of being elected. Yet, many voters choose to support underdogs and we still understand little about their motivations. We argue that voters gauge the support for their preferred party in the voting population from their social networks. When social networks exhibit the characteristics of echo chambers, a feature observed in real-life political networks, voters with a strong preference for an underdog tend to overestimate their chances of winning. We test this claim with voting experiments in which some treatment groups receive signals from a simulated network. We compare the effect of networks with a high degree of homogeneity against random networks. Our findings suggest that homophilic networks generate a net positive effect on the level of support for underdogs, which provides empirical evidence to back up anecdotal claims that echo chambers foster the development of fringe parties.