The Behaviour of Mainstream Parties Towards New Challenger Parties in Parliament – The Effect of Ideological Distance on the Adoption of Challenger Parties’ Positions

Many party systems in Western Europe have experienced considerable change during the last decades. Amongst them is the successful entry of new challenger parties into national parliaments. This is confronting the existing parties with the task of how to behave towards these challengers. The effects of these changes in the political landscape on mainstream parties have been an increasingly studied field in political science. Whereas previous studies have focused on the electoral area, I will turn to the effect on party behaviour in parliaments. This yields the opportunity to not only study reaction patterns over time, but also, to test common hypotheses on the positioning of parties with a far more detailed dataset. For reasons of comparability, I focus on the reaction of mainstream parties towards right-wing populist parties in the field of European integration. I build on recent theoretical developments and use an integrated framework combining elements from positional and salience theories of party competition. I hypothesize and test whether mainstream parties with a less pro-European position will move closer towards the position of Eurosceptic challengers. And if mainstream parties with a more pro-European ideology react to this movement with a more adversarial strategy or if these position changes are related to government-opposition dynamics. This work is not only theoretically driven by setting the focus on parliamentary behaviour. It is also methodologically driven by using new text as data approaches to measure the positioning of parties. Analysing full transcripts of parliamentary speeches from a database that covers key legislative chambers, I describe how mainstream parties change their position over time once challenger parties enter the parliament. As the database spans the last twenty to thirty years in six European countries, it offers the possibility to make comparisons both between and within countries. Estimating Wordshoal scores provides the appropriate method to measure these changes. I analyse the change in positioning of the mainstream parties after the entry of challenger parties, taking into account the mediating effect of public opinion as well as past election results. Even though the focus of this work is on the topic of European integration, the outcome of this study will deliver results that will be extended in upcoming studies and give a first hint towards the handling of mainstream parties with challenger parties in parliament. The study provides important knowledge whether it is possible to generalize reaction effects across countries and which factors mediate these reactions. Therefore, it has implications for the parliamentary behaviour of parties as well as how to analyse it.