Strategies to counter political misinformation have largely focused on demand-side approaches, equipping voters to avoid, detect, fact-check, or report false information. However, since elites play a central role in disseminating misinformation, governments have increasingly adopted supply-side strategies, imposing legal penalties on individuals who spread falsehoods. Brazil’s new regulations, introduced after the storming of the presidential palace in 2023, exemplify this trend. Beginning in 2024, a key government body systematically monitors the online behavior of candidates and prosecutes offenders.

This paper examines whether informing candidates about these penalties reduces the flow of misinformation they endorse. Beyond this, we test whether alternative messaging strategies can achieve similar effects. Using a field experiment with almost 3,000 mayors running for reelection in Brazil, we evaluate the impact of different messaging strategies on the online behavior of candidates. Additionally, we conducted a survey experiment with city council candidates to investigate the mechanisms behind these behavioral changes.

Our findings show that informing candidates about penalties significantly improves their discernment of misinformation, leading them to avoid sharing false content at higher rates. However, this approach also reduces the overall volume of social media activity, indicating a potential chilling effect. Importantly, we find that gentler, nudge-based interventions may be equally effective in reducing misinformation without suppressing overall engagement.

These results have significant implications for governments and online platforms seeking sustainable approaches to combating misinformation. While strong supply-side measures can mitigate misinformation, they may inadvertently deter broader social media participation, raising questions about their long-term impact on democratic discourse.