Can interest groups shape public opinion? Experimental evidence from Germany and the UK

Abstract Interest groups spend large amounts of money on public campaigns, but do these outside lobbying strategies change public opinion? Several recent studies investigate this question, but come to different conclusions. We integrate existing approaches into one factorial design and conduct a well-powered survey experiment across two countries. We randomize type of interest group support and message medium in support of two prominent climate policies. Our results suggest that interest group messages can have a short-term influence on public opinion. However, the effects are not different from policy messages without interest groups, are not larger for messages from interest group coalitions, and are only effective for subsidies, but not for increases in taxation. In addition, we investigate the mechanism linking outside lobbying and public opinion and find that outside lobbying signals higher support for policies among the public. Our results have implications for comparative studies of interest group strategies.