Do terrorist attacks polarize politicians? Evidence from the European parliamentary speeches on migration

Abstract We study the effect of terrorist attacks on the European Parliament (EP) migration discourse. First, using an LLM model, we develop an original dataset on the sentiments of all parliamentary speeches concerning migration for 2009–2019, building on a novel dataset by Sylvester et al. (2023). Second, following Brodeur (2018), we employ a causal identification strategy using quasi-natural randomization in the success or failure of terrorist attacks. We find that a successful terrorist attack has heterogeneous effects on migration sentiments conditional on the political position of the speaker: left-wing speeches become substantially more favorable toward migration after successful attacks, while speeches by right-wing politicians become moderately more negative. Politicians of different ideologies adjusting migration-related sentiment in a direction aligned with their pre-existing partisan positions indicate an increasing polarization among policymakers as a direct consequence of terrorism.