Political parties across the EU have formed more grand coalitions over the last two decades, including in countries with no prior experience of such alliances. At the same time, new and radical parties have surged, signaling growing fragmentation in European politics. This study investigates how mainstream and new parties fare electorally when they enter or leave grand coalitions.

📊 Tracking Grand Coalitions Across Two Decades:

• Analysis covers grand coalition formation in EU member states over the last twenty years.
• Emphasis on the spread of grand coalitions even in systems without prior experience, set against a rise in new and radical parties.

🔎 What Was Compared:

• Electoral performance of mainstream parties that enter grand coalitions.
• Comparison of major and minor grand coalition members' vote fortunes in subsequent elections.
• Examination includes parties that both join and leave grand coalitions, and considers new party dynamics alongside mainstream behavior.

📈 Key Findings:

• There is no evidence that mainstream parties form grand coalitions in direct response to negative election results; parties do not appear to enter grand coalitions after losing votes.
• Mainstream parties that participate in grand coalitions face an electoral penalty in the following election, but this penalty is smaller than reported in earlier studies.
• The post-grand coalition penalty affects both major and minor coalition members.

💡 Why It Matters:

• Findings refine understanding of party competition in fragmented electoral landscapes and temper prior claims about the electoral costs of grand coalition participation.
• Results offer practical insight into the strategic choices mainstream parties make amid rapid changes in the EU’s party system, especially when balancing coalition stability against voter backlash.