The influence of Eurosceptic challenger parties on mainstream party behaviour: Is oppositional behaviour contagious?

Previous research has looked at how Eurosceptic challenger parties can cause mainstream parties to change their policy positions and bring about adjustments to their programmes. We explore whether this contagion effect extends to the parliamentary behaviour of mainstream parties in European Union (EU) affairs. The empirical analysis is based on a large-scale study of 6215 statements made by national parliamentarians in the European Affairs Committee of Sweden between 1995 and 2016. A dynamic panel analysis of the data shows that the oppositional behaviour of Eurosceptic challenger parties has a significant impact on the opposition statements made in EU affairs by mainstream parties. These findings have important implications for the general understanding of factors that drive national EU opposition.