How does the opposition govern under autocracy? Most authoritarian regimes tolerate some degree of internal opposition, allowing it to contest and even take power. Yet we know little about how such power-sharing dynamics affect governance. In this paper, I exploit a unique instance where the opposition won control of political institutions in a prominent electoral autocracy: the 2017 Moscow municipal elections. Using a difference-in-differences design, I find that opposition control of municipal councils reduced the financial returns from office for ruling party deputies. This decrease in earnings comes from opposition-held councils removing rent-seeking opportunities by organizing more competitive procurement, reducing unnecessary budget expenditures, and curbing over-the-top compensation. Using a survey experiment, I then show that voters prefer opposition candidates with municipal governing experience over ruling party ones without it. Even in repressive environments, challenging autocratic rule may be well served by joining rather than boycotting institutions..