Research on the political competence of persons with intellectual disabilities remains sparse, often outdated, and lacking in systematic analysis. Importantly, no empirical study has ever conclusively demonstrated their alleged political incompetence. Yet, the presumption of incompetence—never empirically established—has historically justified, and continues to justify, restrictions on voting rights. The data provided in this dataset addresses two major gaps in the literature. First, it provides an evidence-based assessment of the political competence of individuals with intellectual disabilities in the context of Swiss direct democracy. Second, it examines how linguistically simplified political materials affect their political competence. These objectives are closely intertwined: the ability to express political competence, and ultimately to make autonomous political decisions, depends on the broader context in which citizens operate. The research project in which this data was collected is grounded in a relational conception of autonomy. Among the external conditions shaping political autonomy, access to accessible information plays a decisive role. This issue is especially pressing for citizens with intellectual disabilities. The originality of this dataset lies in both its empirical analysis of the political capabilities of persons with intellectual disabilities and its participatory design: political representatives collaborated in producing simplified short videos presenting their political views, while persons with intellectual disabilities verified the accessibility of these materials. By reassessing the political competence of persons with intellectual disabilities, this paper reopens broader debates on the scope of the electorate, the conditions of access to it, and the minimal competencies—if any—that should be required of citizens.