To realize sustainability transitions, there is a need for broad societal support. A study now shows that images can be influential in building that support, even in the case of policy decisions to invest in greener urban transportation, which more sceptical citizens would typically not endorse.

The influence of visualizations on decision-making about controversial policy issues is increasingly recognized in the political and policy sciences. In this paper, we explore how combinations of visuals and text on Twitter (now X) lead to the formation of networks of actors sharing similar textual and visual framings about a policy issue in an online setting, which we conceptualize as Multimodal Online Discourse Coalitions (MODCs). MODCs struggle over the meaning of contested policy issues. We examine multiple MODCs in 2018 in the context of the regulatory decisions in that year about CRISPR-Cas gene editing technology in the USA, Mercosur, and the EU. Based on an SNA and a qualitative visual and discursive analysis in three languages on Twitter in 2018 (covering in total ~ 427 k Tweets), we show that MODCs in English and Spanish focused on technocratic aspects of CRISPR-Cas, resembling the regulatory decisions in the USA and Mercosur. In Europe, next to technocratic MODCs, an MODC in French formed around ethical/normative framings of the consequences of CRISPR-Cas applications, using visuals of embryos to represent “GMO babies.” These visuals were emotional triggers in their framing of CRISPR technology. The ethical/normative framing reflected the argument brought to the CJEU by a group of French actors involved in the court case which categorized CRISPR-Cas as a GMO technology in the EU. These results suggest that the French MODC and their visualization was of influence on the EU decision-making process; however, more research is needed to verify the role of this online debate in the decision-making process.