How can we understand public opposition to reforms that aim to reduce greenhouse gas emissions and induce a clean-energy transition? Previous work documents that exposure to the material costs of a policy reform can generate public disapproval, but much less is known about the extent to which voters anticipate the costliness of climate reforms and voice opposition already in the policy formation stage that precedes actual implementation. We study these dynamics in the context of Germany in the spring of 2023, when the government coalition announced an amendment to the Gebäudeenergiegesetz (buildings energy act, “GEG”). This amendment, which was advanced by the Green Party, should accelerate the replacement of fossil fuel-based heating systems with electricity-based systems in residential buildings. We study how the announcement of this reform affected public approval of incumbent parties and politicians, led to an electoral realignment toward the right-wing anti-environmental party AfD, and caused a public backlash, more broadly, for the support of environmental policies. We examine our argument at the individual, regional, and national level using an integrated observational and experimental research design. We use individual-level panel data, local election results, and high-frequency polling data in combination with difference-in-differences estimators to explore how expected exposure to policy-related costs affected support for incumbent parties, the Green Party, the radical right, and climate action more generally. We further investigate the sources of climate policy resistance by exploring voters' narratives and (mis)perceptions using a survey experiment and AI chatbot-based qualitative interviews.