1. Introduction and theoretical framework Silja Häusermann and Herbert Kitschelt; Part I. Voter Flows and Electoral Potentials: 2. The changing geography of the social democratic vote Jane Gingrich; 3. Losing the middle ground: the electoral decline of social democratic parties since 2000 Tarik Abou-Chadi and Markus Wagner; 4. Who continues to vote for the left? Social class of origin, intergenerational mobility and party choice in Western Europe Macarena Ares and Mathilde M. van Ditmars; 5. Lost in transition: Where are all the social democrats today? Daniel Bischof and Thomas Kurer; 6. Social democracy in competition: voting propensities, electoral potentials and overlaps Silja Häusermann; Part II. Considerations of Choice: Motivations and Preferences: 7. Vote switchers and social democracy in contemporary knowledge capitalism: voter rationales signal strategic dilemmas of social democracy Herbert Kitschelt and Philipp Rehm; 8. Labor unionization and social democratic parties Silja Häusermann, Herbert Kitschelt, Nadja Mosimann and Philipp Rehm; 9. Old left, new left, centrist or left national? Determinants of support for different social democratic programmatic strategies Tarik Abou-Chadi, Silja Häusermann, Reto Mitteregger, Nadja Mosimann and Markus Wagner; Part III. Determinants of Electoral Outcomes for Social Democratic Parties and the Left: 10. Voter responses to social democratic ideological moderation after the third way Jonathan Polk and Johannes Karreth; 11. Social democracy and party competition: Mapping the electoral payoffs of strategic interaction Herbert Kitschelt and Philipp Rehm; 12 The electoral consequences of centrist policies: fiscal consolidations and the fate of social democratic parties Björn Bremer; 13. Leadership turnovers and their electoral consequences: a social democratic exceptionalism? Zeynep Somer-Topcu and Daniel Weitzel; 14. Conclusions Silja Häusermann and Herbert Kitschelt.