Do Donors Punish Extremist Primary Nominees? Evidence from Congress and American State Legislatures

Fundraising is a critical element of legislative elections, yet problems of measurement and strategic candidate emergence have prevented researchers from evaluating how running extremist candidates affects parties’ fundraising prospects. This article combines an original candidate ideology scaling with a regression discontinuity design in primary elections in Congress, 1980–2022, and state legislatures, 1996–2022, to assess whether donors punish extremist nominees in general elections. I find that the “coin-flip” primary nomination of an extremist over a more moderate opponent decreases their party’s share of general-election contributions by 7 percentage points in the median contest and 18–19 percentage points when the ideological contrast between candidates is largest. This financial penalty is larger among corporate PACs than individual donors and is driven symmetrically by donors withdrawing support from extremist nominees and rallying behind their opponents. Applying a complementary panel-based identification strategy, I replicate these core findings and further document that the financial penalty to extremist nominees has fallen by nearly half since 2000. Overall, these results show how general-election donors act as a marked, yet waning, moderating force in American politics when parties run extremist candidates.