Campaign spending in mixed member proportional systems: How political and institutional context shapes party strategy

Despite extensive work on local campaign spending, existing research has mostly focused on campaign expenditures in majoritarian systems, while disregarding spending patterns under other institutional arrangements. To help fill this gap, we study how parties allocate their funds in mixed member systems. Based on the notion of contamination between the electoral tiers, we argue that spending is less targeted toward winning the district mandate under mixed electoral rules than would be expected in a pure majoritarian system, as parties stand to benefit from a visible district contender even when they lose the race. Studying candidate survey data collected over the course of four German federal elections between 2009 and 2021, this expectation is confirmed. While the general pattern is evident in all four elections, the shifting political and institutional context of campaigning in Germany has changed party strategies. A more proportional electoral system, along with a more fragmented party system has put a nominal mandate within reach of smaller parties, while larger parties are less sure about winning in their former strongholds, prompting parties to move to more targeted spending on competitive seats.