Diffusion

This project speaks to research on policy diffusion and transnational party learning (Dobbin et al. 2007; Weyland 2005), the multilevel governance literature on EU integration and party behavior (Hix 2002; Hooghe & Marks 2001), and studies of party organization and nonlegislative parliamentary activities (Green‑Pedersen 2010; Proksch & Slapin 2011).

Although the policy diffusion literature examines how policies and ideas travel across jurisdictions, it largely treats states as unitary actors. Little is known about how political parties—especially across national and European levels—engage in policy diffusion and issue transfer, and about the role of transnational alliances and party networks in shaping domestic and EU‑level agendas.

How we addressed it

• Conceptual synthesis: We developed a pluralistic framework of party policy diffusion and issue transfer in the European multilevel space, distinguishing key actors, objects, and mechanisms of diffusion.
• Spatial econometric analysis: We applied spatial regression models to Comparative Manifesto Project data from 26 Western European democracies (1977–2016) to test how EP party group memberships drive ideological diffusion among national parties.
• Dyadic panel analysis: We constructed a monthly dyadic dataset of written parliamentary questions by Danish MPs and MEPs (1999–2009) to examine when and how policy issues transfer across national and European parliamentary venues.

Key Findings

1. Transnational alliance effects: Parties sharing an EP party group exhibit two‑to‑three times stronger short‑ and long‑term ideological imitation than parties outside the group.
2. Multilevel policy issue transfer: Policy issues transfer regularly between national and European venues—occurring in 15 % of monthly party dyads—and predominantly within parties sharing the same brand.
3. Directional agenda‑setting: Transfers are more likely from the domestic to the EU level, especially in policy areas where the EU holds substantial legislative authority.
4. Conceptual pluralism: Diffusion unfolds across principles, aims, and concrete policies, underscoring the need for combined quantitative (spatial models, text analysis) and qualitative approaches.

Implications

For practice: Party strategists and policymakers should recognize that EP party group memberships exert a powerful influence on domestic platforms and issue priorities. While leveraging transnational networks can enhance policy coherence and expertise sharing, parties must guard against echo‑chamber effects that stifle innovation and reduce responsiveness to local constituents.

For social science: This work demonstrates the need for pluralistic methodological toolkits—combining spatial econometrics, dyadic panel analysis, and qualitative case studies—to capture the multifaceted nature of party policy diffusion. Researchers should refine measures to distinguish the diffusion of principles, aims, and concrete policies, and explore the democratic implications of convergence across parties.

Publications

• Senninger, R., Bischof, D., & Ezrow, L. (2021). “How transnational party alliances influence national parties’ policies.” Political Science Research and Methods.
• Wolkenstein, F., Senninger, R., & Bischof, D. (2020). “Party policy diffusion in the European multilevel space: what it is, how it works, and why it matters.” Journal of Elections, Public Opinion and Parties.
• Senninger, R., & Bischof, D. (2018). “Working in unison: Political parties and policy issue transfer in the multilevel space.” European Union Politics.