Seeing like a district: Understanding what close-election designs for leader characteristics can and cannot tell us

Abstract

Many influential political science articles use close elections to study how important outcomes vary after a certain type of candidate wins, such as a Democrat or a Republican. This politician characteristic regression discontinuity (PCRD) design offers opportunities for inferential leverage but also the potential for confusion. In this article, we clarify what causal claims the PCRD licenses, offering a rigorous causal analysis that points to three principal lessons. First, PCRDs do nothing to isolate the effect of the politician characteristic of interest as apart from other politician characteristics. Second, selection processes (regarding both “who runs” and “which elections are close”) can generate and exacerbate such confounding, as noted in Marshall (2024). Third and more fortunately, this approach does make it possible to estimate the average effect of electing a leader of type “A” vs. “B” in the context of close elections, treating the units as districts, not leaders. We also suggest a set of tools that can aid in falsifying key assumptions, avoiding unwarranted claims, and surfacing mechanisms of interest. We illustrate these issues and tools through a reanalysis of an influential study about what happens when extremists win primaries (Hall 2015).