Literature often presents coproduction as a policy strategy used by the public sector when it finds itself limited in its ability to provide services. This argument rests on a central yet empirically unexplored assumption: that policymakers become more supportive of coproduction when facing a risk of service decline. We test this assumption using a preregistered two-by-two survey experiment on 514 elected politicians in Danish local government. Findings suggest that policymakers are, indeed, more supportive of coproduction when facing a risk of service decline than when facing service stability. Policymakers are also more supportive of coproducing complementary service tasks than core service tasks and associate the latter with an increased risk of political costs. These findings not only support a central claim in the coproduction literature but also emphasize how the risk of service decline may serve as a policy window for adopting coproduction in the public sector.