“…Second, and closely related to the question of how contributions from interest groups affect legislative behavior, are the questions of why donors contribute to which campaign and how contributions increase the probability of being elected. Regarding the former, theoretical models have been developed to analyze the contributors' rationale under different institutional settings (see, e.g., Aranson and Hinich ; Fang, Shapiro, and Zillante ) complemented by a growing empirical literature on the various possible motives of donors (see, e.g., Barber ; Bonica ; Gordon, Hafer, and Landa ). With regard to the latter question, a substantive number of studies have empirically investigated the relationship between campaign contributions and election probabilities (see, e.g., Gerber ; Jacobson , ; and recently Spenkuch and Toniatti ).…”