Why Winning Local Office Turns Outsider Parties Into Governing Partners

Why Do Challenger Parties Gain Power?

Authors Frederik Hjorth, Jacob Nyrup, and Martin Vinæs Larsen ask how challenger parties—those without prior government experience—manage to break into governing coalitions. This question matters because challenger parties have reshaped politics across Europe, yet scholars still debate the processes that move them from outsider status to partners in government.

Cross-National Patterns Point to Office Holding

Using cross-sectional national-level data, the authors show a clear association: challenger parties that hold elected office are more likely to enter government later. This broad pattern motivates a closer look at whether office holding itself causes greater access to power, or whether both are driven by other factors.

Causal Test: Regression Discontinuity on Danish Local Councils

To establish causality, Hjorth, Nyrup, and Larsen assemble an original dataset covering more than 2,500 local elections and 15,000 committee assignments in Denmark. They apply a regression discontinuity design that leverages narrow wins and losses for committee seats to isolate the effect of legislative incumbency. Main causal finding:

• Legislative incumbency for challenger parties increases their probability of entering government in the following electoral term.

How Office Holding Changes Challenger Parties

The authors combine the quasi-experimental evidence with survey data from candidates to explore mechanisms. The candidate surveys show that challenger parties who hold office tend to:

• Shift to more moderate policy positions, and
• Adopt more mainstream political language.

These behavioral changes are consistent with a moderation mechanism: holding office pulls challengers toward the political center and makes them more palatable coalition partners.

Why This Matters for Party-System Change

The study identifies a concrete path by which outsider parties convert electoral opportunity into actual governing power: by winning and occupying offices, they moderate and thereby reduce barriers to coalition inclusion. The findings illuminate centripetal forces in party systems and help explain how disruptive parties can become part of the governing mainstream—insights relevant to scholars of parties, coalitions, and democratic representation.