How transnational party alliances influence national parties' policies

Previous research reports that parties in established European democracies learn from and emulate the successful election strategies of foreign incumbents, i.e., successful parties are influential abroad. We theorize that—in addition to incumbency (or success)—exchange takes place through transnational party alliances in the European Union. Relying on party manifesto data and spatial econometric analyses, we show that belonging to the same European Parliament (EP) party group enhances learning and emulation processes between national political parties. Estimated short- and long-term effects are approximately two and three times greater when foreign incumbents are in the same EP party group compared to other foreign incumbents. Our results have implications for our understanding of how transnational party groups influence national parties’ policy positions.