Territorial divisions are commonly believed to dominate the international realm, supposedly leaving no room for ideological distinctions to take shape. However, the formation of over fifty transnational political groups (TPGs) across thirteen international parliaments challenges this assumption, calling into question the previously accepted insignificance of ideology beyond the boundaries of the nation-state. Previously unexplored in comparative perspective, this paper investigates TPGs’ puzzling existence and delineates the conditions for their emergence within international parliaments. The theoretical argument is that homogeneity across the member states of the international parliament along three dimensions – political systems, economic development levels and geographical proximity – fosters the creation of transnational political groups. Results from regression analysis on time series cross-sectional data lend support to the theory. With the rise of international parliamentary institutions and their increased involvement in supranational decision-making over time, it becomes highly important to understand how they organize as well as the implications of their institutional designs.

人们普遍认为，领土划分在国际领域占据主导地位，据认为没有给意识形态差异留下形成的空间。然而，十三个国际议会中五十多个跨国政治团体（TPG）的形成挑战了这一假设，使人们对先前公认的超越民族国家边界的意识形态的微不足道提出了质疑。本文调查了 TPG 令人费解的存在，并描述了它们在国际议会中出现的条件，此前从未从比较角度进行过探索。理论上的论点是，国际议会成员国在政治制度、经济发展水平和地理邻近性三个维度上的同质性促进了跨国政治团体的产生。对时间序列横截面数据进行回归分析的结果为该理论提供了支持。随着国际议会机构的兴起及其对超国家决策的参与程度不断增加，了解它们的组织方式及其制度设计的影响变得非常重要。