Electoral Rules Shape Japanese Candidates' Ideological Positions: A Counterintuitive Look

Japan's electoral reform in 1994 sparked debate about how candidate positioning adapts. This study analyzes ~7,500 election manifestos using quantitative scaling to estimate ideology across eight House of Representatives elections. We find a clear pattern: candidates' positions converge dramatically under single-member districts (SMDs), while diverging significantly within multimember districts (MMDs). When intraparty competition is absent in MMDs, partisan alignment becomes stronger - the opposite effect previously expected from spatial theories.

🔍 Data & Methods

• Analyzed ~7,500 Japanese election manifestos post-reform.
• Used advanced quantitative scaling to measure ideology objectively.

📊 Key Findings

• Candidates move ideologically toward the center in Single-Member Districts.
• They diverge dramatically within Multi-Member Districts (MMDs).
• Without intraparty competition, candidates in MMDs align even more strongly with their partisans.

💡 Why It Matters

This nuanced result clarifies the relationship between electoral systems and Japanese political behavior. The divergence without copartisans challenges conventional spatial theory expectations.