Electoral Management Bodies (EMBs) are commonly established to increase electoral legitimacy by designing, implementing and/or enforcing rules surrounding nominations, polling, voting, and tabulation. Globally however, EMB design, governance, and efficacy vary considerably. Utilizing four EMB data sources, this article asks (1) to what extent do EMBs form a new pillar of constitutional governance; and (2) how effective are they in managing and increasing the legitimacy of elections? We begin by detailing the global diffusion of EMBs, temporally and geographically, together with trends in governance methods, constitutionalization, and degrees of autonomy and capacity. We then turn to examine the extent to which existing EMBs are effective, empirically testing a global sample of states on two measures associated with electoral legitimacy. Four results of our analyses stand out. First, independent EMBs are most abundant in democratizing regions, including Latin America and the Caribbean, Sub-Saharan Africa, and South Asia. Second, while EMBs are increasing in number, only a slight majority of states enshrine these institutions in their constitutions. Third, while independent EMBs are the most common systems, autonomous bodies are largely found in democracies. Finally, EMBs characterized by greater degrees of autonomy and capacity are associated with lower levels of both electoral violence and concerns regarding electoral legitimacy.