In 2015, President Obama introduced the Clean Power Plan (CPP), a federal plan aimed at reducing the production of carbon pollution from power plants. In response, some used legal action to try and stop the plan, while others supported the plan and proceeded with plans for its implementation. This research investigates responses taken by state government in terms of legal remedies and planning for implementation, and what explains those responses. Findings suggest that partisanship plays a key role. Specifically, the partisanship of the attorney general is correlated with the legal response, and the governor with implementation planning. Coals, and perhaps renewables, also seem to play a role, even controlling for partisanship. There is only weak evidence for the effect of policy experience and none for the estimated cost of the policy. The article concludes by discussing the implications of these results for the future of climate policy in the United States.