Towards Measuring Party Ideology Beyond Unidimensional Competition: Examples from Western European Manifestos in the 2010s

This paper asks whether it is possible to correctly locate party ideological positions through existing indexes based on manifesto data, when the assumption of a unidimensional space of electoral competition does not hold a priori. It demonstrates that in Western Europe during the 2010s party ideological positioning is better and more validly represented by a two-dimensional structure, and therefore more adequately measured by instruments that capture both axes of this plane. It does so, based on a comprehensive theoretical framework, by deductively developing scores of economic and cultural left-right positioning and empirically comparing their measurements with those of the Manifesto Project’s (MARPOR) ‘rile’ index, for several Western European elections in the 2010s. This investigation is extremely relevant for understanding the innovative electoral strategies adopted by political formations such as populist radical right and 'left-authoritarian' parties in contemporary Western European politics. Therefore, this paper challenges the assumption of a unidimensional party competition structure in the analysed spatial-temporal context and, especially, starts the fundamental methodological debate concerning how to best develop MARPOR-based indexes that appropriately measure party ideological positions in a plane of competition.