What explains the varying ideological profiles of social democratic parties in contemporary Western Europe? And why have some still accepted austerity after the Great Recession? This book argues that the answer lies primarily in structural conditions: the context-specific configurations of external constraints – economic globalisation, regional economic integration in the Eurozone, and sovereign debt – that shape the political room available to social democrats when defining their electoral programmes. Drawing on empirical evidence from 20 Western European countries between 1990 and 2019, and combining cross-national quantitative analysis with in-depth qualitative evidence on party rhetoric, the book develops and rigorously probes a configurational structural explanation for ideological differences within the social democratic party family. The findings carry urgent implications: where external constraints are most pressing, genuine ideological renewal may be structurally precluded. A must-read for scholars and practitioners concerned with the future of centre-left politics and the state of representative democracy.