How global regimes diffuse in space – Explaining a missed transition in San Diego's water sector

•There is a need to study how regime rationalities are constructed, diffused and reproduced across geographical contexts and scales.•We introduce a conceptual model to analyze transformative opportunities and regime diffusion activities by powerful actors.•The framework is applied to a case study of a missed transition in the water sector in San Diego.•We deploy a mixed methods approach combining Socio-Technical Configuration Analysis (STCA) and expert interviews.•Regime diffusion is achieved by strategic combinations of discursive and substantive system reconfiguration activities.