This book explores negative emotions like anger, fear and grief as important drivers of political action. It examines how treating these feelings as medical problems affects society. Drawing on the political thought of Hannah Arendt, the book develops an original understanding of political emotions as fragile and vulnerable to attacks disputing their relevance to public life. It presents and analyses four case studies of emotional politics in the UK, ranging from assertions that UKIP supporters were emotionally primitive to diagnoses of anxiety disorder in the Brexit referendum's aftermath. It demonstrates how ideas of emotion and mental disorder might be used to both empower and disempower people politically.