Legislatures are a cornerstone of representative democracy at the local, subnational, national, and even supra-national levels. Electoral systems determine how votes are transformed into legislative seats. Because of this, what legislators must do to get re-elected is shaped by electoral rules. The impact of electoral incentives goes beyond behavior, potentially shaping the rules and procedures of the legislature itself. This chapter analyzes theories and evidence that link legislative organization to members’ electoral incentives. However, not all legislative structures have a clear electoral basis. As this chapter suggests, the relationship between electoral systems and how a legislature chooses to organize itself is a conditional one.