This article analyzes the impact of electoral rules on legislators’ rate of vote defection from their party position in legislatures while accounting for how party-leadership strength mediates this impact. To this end it looks at the effect of the 2008 Romanian electoral reform. The reform shifted the electoral system from a closed-list proportional representation to one in which all candidates run in single-member districts. The analysis finds that because party leaders have maintained their leverage intact, the impact of the reform was minimal, with legislators being more likely to defect in less important votes only, in which party leaders allow defection. Also, after the reform legislators are more likely to use other means to impress their voters, such as legislative initiation and cabinet questioning. These forms of behavior are more accepted by party leaders.