Why do some cities adopt more renewable energy than others? This mixed methods study examines the effect of linking ties between companies and mayors, to quantify the effect that a well connected city mayor can have on their city's renewable energy transition. We draw on the case of sizable cities (at least 30,000 residents) in the US states of Massachusetts and the Japanese prefecture of Chiba. We catalogue instances of mayoral support for renewables and specific companies over the last ten years drawing from online newspapers and government documents, statistical modeling, and case studies of key mayors. Mayoral support and ties to renewable power greatly improve solar adoption, but that the strength of grassroots social capital in these cities can strengthen or shackle mayors' efforts, depending on the type of social capital. By highlighting the role of mayors in renewable energy, we hope to clarify in what situations mayors can make a difference in helping cities transition to renewable energy.

Data will be released for replication upon publishing.