Studies that emphasize the importance of legislative electoral systems for campaign finance mostly fit into one of two groups. One literature identifies consequences of electoral systems that foster intraparty competition, including high levels of campaign spending and campaign finance–motivated pork, particularism, and political corruption. The second literature studies “spending effects” (i.e., vote-share gains per unit of expenditure), especially whether they differ between incumbents and challengers. Although both literatures pay some attention to how electoral systems affect campaign financing at the district level, that subject is poorly understood. This chapter emphasizes two topics that merit study: how electoral systems influence spending-votes patterns among incumbents and how electoral coordination may concentrate funds on only M + 1 candidates per district.