Why Electoral Coalitions Benefit Weaker Partners More

📌 What This Paper Asks

The choices party leaders make about forming electoral coalitions shape the alternatives voters face. Existing knowledge is limited about the tradeoffs coalitions impose on potential partners, how coalitions change the strategic responses of competing parties, and their net effect on election outcomes.

🧭 How the Analysis Was Conducted

A structural model of electoral competition is developed and estimated that explicitly incorporates two strategic margins:

• Parties can form coalitions to coordinate candidate nominations.
• Parties invest in campaign activities to support their candidates.

The model is estimated using district-level data from the 2012 Mexican Chamber of Deputies election, leveraging variation in coalition formation across districts. Counterfactual coalition scenarios are simulated to compare equilibrium outcomes under alternative coalition configurations.

📈 Key Findings

• Coalition formation generates measurable equilibrium campaign savings.
• Coalitions produce significant electoral gains, with the benefits accruing disproportionately to weaker coalition partners.
• The structural framework links nomination coordination and campaign investment decisions, enabling analysis of how coalitions reshape strategic choices and electoral outcomes.

🔍 Why It Matters

Coalition decisions by party leaders do more than redistribute campaign resources: they alter who wins and how votes are aggregated, often enhancing the prospects of smaller partners. These results illuminate an important mechanism through which parties shape electoral supply and democratic representation, with implications for party strategy and the study of coalition politics.