Research on interest representation in multijurisdictional polities teaches us much about the activities of a variety of groups that mobilize beyond the state. Scholars, however, largely overlook one type of group: regional authorities. Using data from a telephone survey of senior regional officials in 60 regions and five countries, I investigate the determinants of regional influence in the world's most advanced multijurisdictional polity, the European Union (EU). I find limited regional influence in the EU. Such influence, however, increases with a region's size and with the supranational embeddedness of its top officials. Surprisingly, levels of decentralization play only an indirect role. Hence, two logics appear to drive regional success: (i) a representational logic-as the more populous wield more influence-and (ii) a cumulative advantage logic (the "Matthew effect"). While the representation of the many over the few is in line with democratic principles, the cumulative advantage logic contradicts the EU's stated objective of an ever-closer union.