Book excerpt: Around the world, parties of the left and center-left have been struggling, losing ground to right-wing parties and various forms of reactionary populism. This book brings together a range of leading academics and experts on social democratic politics and policy to offer an international, comparative view of the changing political landscape. Using case studies from the United Kingdom, Germany, Spain, France, Australia and New Zealand contributors argue that despite different local and specific contexts, the mainstream center-left is beset by a range of common challenges. Analysis focuses on institutional and structural factors, the role of key individuals, and the atrophy of progressive ideas as interconnected reasons for the current struggles of the center-left.