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

We conducted a field experiment to study social influences on partisan political participation. We sent letters to 92,000 contributors during the 2012 presidential election campaign. We randomized features of the letters and measured the effects of these variations on the recipients' subsequent contributions. We find 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. Individuals contribute more when they perceive higher average contributions from own-party supporters in their area and contribute less if there is a higher share of own-party contributors.