In December 2005, Italy's mixed-member electoral system was replaced with a system of bonus-adjusted proportional representation. The reform conformed with rational-choice models in that it was imposed by the ruling coalition, which sought to bolster its own power interests. But the case illustrates the impossibility of reducing such power-based motivation to a single goal, such as seat maximization. Power is shaped by many factors, and electoral systems influence many of these. This article develops a theoretical framework for understanding the various power-oriented considerations that may operate in electoral reform. It then analyses the role these played in Italy. It argues, in particular, for the need to take account of coalition dynamics when studying such processes.