Does Climate Action Threaten Democracy? Effects of Carbon Tax Endorsements from Varying Sources in the US and Germany

Climate change exposes a core dilemma of democracy: how to tackle polarizing and long-term crises when system incentives push politicians toward demonstrating immediately visible successes. While a number of climate policies have achieved major emission reductions, structural challenges remain. Electoral cycles, voter preferences, powerful special interests, and the absence of future generations systematically hinder effective long-term policymaking. Attempts to introduce ambitious climate policies have repeatedly triggered public backlash—as observed in France, Mexico, or Germany. Polarization entrepreneurs use climate discourses to intensify societal division and advance their strategic interests. These dynamics have amplified concerns that mere promotion of ambitious climate action risks voter loss and strengthens right-wing populism9, ultimately threatening liberal democracy. Research shows that the messenger matters for the effects of political communication, particularly on polarizing issues. Not only political communicators worry about potentially adverse and polarizing effects of promoting unpopular climate policy. Scientists and science communicators fiercely debate the role they should play in climate communication. While some advocate for a more active, even activist role, others fear that advocating specific policy action undermines their credibility, ultimately threatening the institution of science. Climate activists and NGOs have successfully raised awareness of climate change but have also been criticized for fanning polarization. Theorists argue that deliberative minipublics, a new kind of peer-messenger, might be well-posited to communicate about contested issues, because they are independent, informed, and similar. Minipublics convene randomly selected citizens who hear experts and deliberate intensely on a political issue. We tested preregistered hypotheses about the impact of a pro-carbon tax endorsement on party on attitudes toward populism, democracy, political parties, and the messenger in a series of three survey experiments in the US, plus one in Germany, between 2021 and 2024 (N ≤ 6,000). To test the effect of message sources, we randomly assigned the endorsements to one of four sources: the government, a consortium of scientists, an environmental NGO, and a minipublic. We also included an endorsement without source and a control group. This conference paper will report on the results.