When Business Speaks, Legislators Listen: Experimental and Qualitative Evidence from Brazil

The influence of interest groups on policy making is a central concern in representative democracies, yet identifying causal effects remains a significant challenge. This article argues that legislators respond to informational cues about the economic importance and coalition breadth of interest groups. A field experiment in Brazil, which randomized the receipt of printed and WhatsApp messages from a pro-reform business organization, reveals that legislators are more likely to vote in favor of the group’s position when its membership size, economic importance, and sectoral reach are emphasized. A survey experiment with lobbyists supports this mechanism, showing that messages highlighting group characteristics increase legislators’ expected engagement and support. In-depth interviews with key political figures—including a former president, ministers, and deputies—further corroborate these findings. This study contributes to the literature on informational lobbying and cue-based persuasion by employing realistic experimental treatments and mixed-methods evidence.