This book examines and explains the Center-Left's political decline since 2008, whilst analyzing the factors that account for its sagging electoral and popular support, losing voters both to the Far-Left, the Far-Right, and abstentions. Focusing on the era since the 2008 financial crisis in particular, while also charting the historical genealogy that led to the current impasse, the book examines how, when and why the collapse of Europe's Center-Left occurred. Moving beyond existing and slightly dated accounts, the contributors explore why Social Democrats lack compelling answers to pressing current policy challenges. Faced with a decline in its core clientele, namely blue-collar workers, the Center-Left is being outflanked and risks permanently jeopardizing its erstwhile status as representing a catch-all party. Exploring one of the more pressing and timely political puzzles of the contemporary political scene in Europe, the book identifies six factors that have driven the decline of the Left and examines them systematically across eight countries: France, the United Kingdom, Germany, Sweden, Italy, Austria, the Netherlands, and Denmark. This book will be of particular interest to both scholars and students of social democracy, political parties, and the politics of the Left and more broadly to those interested in European and comparative politics, governance, and contemporary history.