The Brexit referendum was a pivotal moment in British politics. Tribal Politics argues this is not only because it led to the UK's departure from the European Union, but also because it created two new, powerful, and enduring political identities in the UK: Leavers and Remainers. These new identities rapidly became central to how people saw themselves, others, and the world around them, and they continue to underpin British politics.Tribal Politics explores how these identities were created and why they have proved so resilient in the years following the 2016 vote. It does so by treating the Brexit divide as the result of three contingent factors: issue contestation (intense, high-stakes public conflict), issue expression (individual commitment through voting and political engagement), and issue alignment (the way Brexit cut across traditional party lines). Together, these conditions transformed what had been, for many, a distant policy question into a deep and lasting identity divide.Drawing on political psychology and a wide range of original evidence—including surveys, experiments, and analyses of political discourse—Sara B. Hobolt and James Tilley examine the far-reaching consequences of tribal politics for political attitudes and choices. They show that we dislike, look down on, and discriminate against people because they belong to another tribe, and that we also change our views of reality, our policy opinions, and even our perceptions of democratic legitimacy to better fit our tribal loyalties.While rooted in the Brexit experience, Tribal Politics speaks to the origins and consequences of all types of identity-driven affective polarization. As many democracies around the world confront deepening political divides, it offers timely insights into how a single political moment can spark lasting tribalism and why those tribes so often survive long after that moment has passed.