Darker Blue: How Small Donors Drive Congressional Polarization

Over the previous two decades, campaign contributions from small donors to congressional elections have surged, and new technologies have transformed the process of political fundraising. How does money from small donors change how legislators take positions and behave in Congress? ActBlue is a digital platform that has lowered the non-monetary costs of individual contributions and has processed billions of dollars in donations for Democratic candidates and causes. Using a difference-in-differences design based on staggered ActBlue adoption by House candidates, I find that when candidates join ActBlue, they raise more money from individual donors. This is predominantly driven by growth in small-donor contributions.