Interest groups spend vast amounts on indirectly affecting policy-makers by communicating to the public, but do these outside lobbying strategies actually affect voters’ policy positions? We argue that costlier public messages as well as more diverse interest group coalitions signal higher credibility and are thus more successful in affecting individual policy preferences. Moreover, we expect that the effect of costly messaging and coalitions on preferences is conditional on prior beliefs, trust in the sender, and the distributional consequences of proposed policies. We test our argument using a cross-country survey experiment in Germany, Denmark, and Spain, in which we randomly vary interest group coalition types and strength of public messages in support of two widely-discussed policies tackling climate change: carbon taxation and electric vehicle subsidies. The findings have important implications for the role of interest group coalitions for sustaining public support for climate change policies.