Partisan Interactions : Evidence from a Field Experiment in the United States

Since campaign contributions reveal the actor’s party leanings, they take place in a domain of social observation and are likely to be subject to social effects. We conducted a field experiment to identify some of these social effects. We sent letters to 92,000 contributors from all U.S. states during the 2012 presidential election campaign. We randomized subtle details in those letters to create non-deceptive experimental variation in the probability that the recipient’s contributions were observable to her neighbors, and in the recipient’s perception of the contributions of others. We use administrative data to measure the effects of these variations on the recipients’ subsequent contributions. We show that making an individual’s contributions more visible to her neighbors increases the contributions of supporters of the local majority party, and decreases those of supporters of the minority party. This evidence is consistent with a model of partisan signaling in which individuals treat supporters of their own party favorably and supporters of the opposite party unfavorably. Additionally, we show that individuals contribute more when they perceive higher average contributions from own-party supporters in their area, but not do not react to contributions from opposite party neighbors, which is consistent with social norm theories. Last, individuals contribute lower amounts when they perceive a higher share of own-party contributors, which can be interpreted as free-riding. Taken together, the evidence suggests that partisan interactions play an important role in shaping political participation