The effect of campaign spending, district magnitude and incumbency when electoral rules create districts with old and new voters: the case of Chile in 2017

The impact of campaign spending, generally greater for challengers than for incumbents, is conditioned by electoral rules and incumbency-normally seen as a dichotomous condition. But when an electoral reform changes the composition of districts, a legislator is an incumbent only in the section of the new district. In Chile, the 60 open-list proportional representation 2-member districts used until 2013 were combined to create 28 open-list PR districts for the 2017 election, thus making some legislators enjoy a higher degree of incumbency. With data from 1430 candidates in the 2013 and 2017 legislative elections, we report a nonlinear positive effect of campaign spending on electoral success in all district magnitudes. Campaign spending has a higher impact as the number of open seats increases and a stronger effect for incumbents whose old districts comprise a larger share of the new districts. Campaign spending matters differently for challengers and incumbents given the moderating effect of district magnitude, the number of open seats and the percentage of incumbency.