play both sides of the fence

To aid, support, or engage with both sides of some issue, situation, agenda, competition, etc. Usually used with the implication of doing so in a duplicitous manner to benefit one's own interests or agenda, though not always. She was accused of playing both sides of the fence, acting as a legal adviser for groups trying to legalize recreational cannabis while also serving on the board of several organizations that have tried to quash such actions. Look, I've been playing both sides of the fence in Washington for years, negotiating the rather volatile divide between corporate and political interests very carefully.