Structural Selection and the Erosion of Democratic Resistance in the Republican Party

This study investigates the relationship between political donor networks and legislative voting behavior in the United States House of Representatives across the 117th and 118th Congresses and how this relationship intersects with democratic norm erosion. Using Federal Election Commission contribution records and Voteview roll-call voting data, campaign finance and voting data are transformed into donor similarity and voting similarity networks by Congress, chamber, and party. Quadratic Assignment Procedure regression models test whether donor network overlap predicts voting similarity at the dyadic level, and fuzzy-set Qualitative Comparative Analysis identifies configurations under which donor similarity is sufficient for high voting similarity. Three main findings emerge. Donor network similarity is a significant and ideology-independent predictor of voting similarity among House Republicans but not Democrats, consistent with organizational party theory. This effect is concentrated among ideologically ambiguous Republicans in the 117th Congress and generalizes across the full ideological range of the surviving caucus following the 2022 primary cycle, consistent with a mechanism in which the primary purge is associated with broader donor coordination across the party's ideological spectrum. The most donor-connected Republicans in the 117th Congress were also the most likely to cast pro-democracy votes on the January 6 certification and impeachment roll calls, and the most likely to be eliminated in 2022. These findings support a structural selection argument: donor networks were concentrated around legislators most capable of intra-party democratic resistance, primary elections systematically removed those legislators, and the surviving caucus became more homogeneous and more dependent on donor signals. Structural selection links campaign finance and democratic erosion not by purchasing individual votes but by determining which legislators remain in office to cast them.