Doochun Kim
This study examines the role of political partisanship in shaping state-level renewable energy policy, with a particular focus on the temporal dynamics of Renewable Portfolio Standard (RPS) adoption. It addresses a critical gap in the existing literature by asking whether political ideology affects RPS adoption immediately or only after delayed institutional responses. Using panel data for all 50 U.S. states from 2001 to 2024, this study contributes to the literature by identifying policy lags and structural shifts in renewable energy policy development. Employing fixed-effects panel regression with clustered standard errors, this study finds that contemporaneous Democratic control is statistically insignificant, whereas the two-year lag of Democratic control is positively and significantly associated with a higher probability of RPS adoption. The three-year lag also remains positive, although it is only marginally significant in the preferred specification. These findings support the policy lag hypothesis, suggesting that political influence is mediated by institutional inertia. Electricity prices are positively associated with RPS adoption in some specifications, whereas GDP per capita remains statistically insignificant. In addition, the Hausman test supports the fixed-effects specification, and the Bai–Perron multiple breakpoint test identifies significant structural breaks in 2007 and 2015. Overall, the findings indicate that partisan influence is better understood as a delayed rather than an immediate process. Accordingly, policymakers and stakeholders should account for institutional and regulatory lags when designing long-term energy transition strategies.