Giving to the Extreme? Experimental Evidence on Donor Response to Candidate and District Characteristics

How does candidate ideology affect donors' contribution decisions in U.S. House elections? Studies of donor motivations have struggled with confounding of candidate, donor, and district characteristics in observational data and the difficulty of assessing trade-offs in surveys. We investigate how these factors affect contribution decisions using experimental vignettes administered to 7,000 verified midterm donors. While ideological congruence influences donors' likelihood of contributing to a candidate, district competitiveness and opponent extremity are equally important. Moreover, the response to ideology is asymmetric and heterogeneous: donors penalize more moderate candidates five times more heavily than more extreme candidates, with the most extreme donors exhibiting the greatest preference for candidates even more extreme than themselves. Republicans also exhibit a greater relative preference for extremism than Democrats, although partisan differences are smaller than differences by donor extremism. Our findings suggest that strategic considerations matter, and donors incentivize candidate extremism even more than previously thought.