This study examines how electoral rules influence government composition in established democracies.

* Electoral Systems: Investigates majoritarian versus proportional representation (PR) systems and their impact on governing parties. The finding is clear: countries with PR systems more often elect conservative governments than those using majoritarian rules.

* Mechanisms at Play: Explores three potential reasons for this pattern:

1. Voting Behavior Differences: Hypothesizes that middle-class voters anticipate redistributive policies and are more likely to vote for right-wing parties under majoritarian systems.

2. Geographic Vote Biasing: Proposes that the regional distribution of votes can disadvantage left-leaning parties in translating votes into seats due to large urban district margins.

3. Party Fragmentation Effects: Suggests that more fragmentation among right-wing parties under PR makes it less likely for a single conservative party to gain formateur status.

* Hypotheses Tested: Assesses these hypotheses across the entire post-war period in established democracies.

* Results:

• The first two explanations hold true: majoritarian systems bias against left parties through vote anticipation and geographic effects.

• Party fragmentation, however, does not co-vary as strongly with electoral rules as expected.

This confirms a conservative lean in majoritarian systems while highlighting the complexity of PR impacts.