This article contributes to urban regime theory by analysing the conditions enabling the electoral consolidation of social movement-led left coalitions in Spanish cities after 2015. It uses fuzzy-set qualitative comparative analysis to investigate combinations of economic and political factors influencing regime change across 18 cases. The analysis identifies civic capacity as a necessary condition and finds that no single factor is sufficient. Instead, consolidation results from particular combinations: in smaller cities, high representation in local councils and fiscal capacity compensate for hostile upper-tier governments; in larger cities, intergovernmental allies are more critical. Contrary to expectations, capital mobility plays only a small explanatory role, likely due to Spain’s intergovernmental fiscal transfers. These findings underscore the importance of political-institutional factors – especially civic mobilisation and multi-level alliances – for progressive urban governance.