The plurality rule often limits party competition, favoring two-party systems. However, it remains unclear whether this outcome is primarily due to parties exiting elections strategically or because voters vote strategically themselves.

To address this gap, researchers designed a unique laboratory experiment where participants simulated both parties and voters interacting in real-time electoral scenarios. The results demonstrate that the reduction of fragmented parties under plurality rule occurs more significantly through strategic exits by parties than through strategic voting by individuals.

Our findings highlight the crucial role parties play in shaping competition dynamics within multi-member districts governed by a plurality system. This suggests policymakers should consider party behavior as a primary factor when analyzing electoral fragmentation.