The document analyzes how Brexit contributed to the realignment of British politics based on data from the British Election Study from 2014-2019. It finds that Brexit had a major impact by making Europe the dominant political issue and forming large groups with passionate stances on leaving or remaining. This led to the realignment of both political parties, which shifted their positions on Brexit, and voters, who changed which parties they supported based on their Brexit stance. The polarization was driven both by voters changing their behavior and parties adopting clearer Brexit positions.