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.

Does ideological polarization undermine or strengthen people’s principled support for democracy? In this study, we suggest that different manifestations of ideological polarization have different implications in this respect. Using data from 11 surveys conducted with representative samples of the adult populations of a group of liberal democratic countries, part of the Comparative National Elections Project, we look at how people’s level of ideological extremism and their perceptions of ideological polarization in their countries’ party systems are related with their support for democracy. We show that citizens who hold more extreme ideological positions are indeed less supportive of democracy and that such a negative relationship is strengthened as citizens’ extremism increases. However, we also show that the citizens who display higher levels of principled support for democracy are those who perceive parties to be neither too distant nor too close to each other in ideological terms. In other words, while a very polarized partisan supply seems to undermine popular commitment with democracy, very low polarization may have similar consequences.