Incumbency Advantage
Incumbency as a Source of Spillover Effects in Mixed Electoral Systems
In Hainmueller and Kern (2008), this study demonstrates that incumbency generates spillover effects in Germany’s mixed electoral system. Using a quasi-experimental research design that allows for causal inferences with fewer assumptions than traditional regression models, the study finds that incumbency increases proportional representation (PR) vote shares by 1.4–1.7 percentage points. Simulations of Bundestag seat distributions reveal that these spillover effects are significant enough to shift parliamentary majorities, highlighting the broader political implications of incumbency advantages.
Assessing the External Validity of Election RD Estimates: An Investigation of the Incumbency Advantage
In Hainmueller, Hall, and Snyder Jr (2015), the regression discontinuity (RD) design is used to estimate the incumbency advantage in tightly contested elections. While RD provides robust local estimates for 50-50 races, its applicability to less competitive districts has been uncertain. This study introduces a novel method to extend RD estimates to elections where the winner secured up to 57.5% of the two-party vote. The findings confirm that the incumbency advantage remains consistent across both competitive and less competitive races, enhancing the external validity of RD estimates.
