Previous research has found that political traits have some degree of genetic basis, but researchers have had less success unpacking the relationship between genes and political behavior. We propose an approach for examining this relationship that can overcome many of the limitations of previous research: polygenic indices (PGIs). PGIs are DNA-based individual-level variables that capture the genetic propensity to exhibit a given trait. We begin by outlining how PGIs are derived, how they can be utilized in conventional regression-based research, and how results should be interpreted. We then provide proof of concept, using data on over 50,000 individuals in four samples from the U.S. and Sweden to show that PGIs for health and psychological traits significantly predict measures of political participation, even within families. We conclude by outlining several ideas and providing empirical examples for researchers who may be interested in building on the PGI approach.