How is electoral competition structured in Europe? This fundamental problem lies at the core of democracy, as popular sovereignty depends on the existence of a real policy choice, and requires the most preferred alternative being selected and implemented (Dahl 1956). However, there is no consensus yet regarding the actual occurrence of this mechanism of responsive electoral competition (Schumpeter 1942). I develop a new empirical design to test whether a structure of electoral competition in Europe actually exists, based on the idea that greater party system polarization should be associated with a smaller propensity for voters to switch between electoral blocks. To do so, I identify two potential loci of electoral competition in Europe: the left-right dimension (Downs 1957; Bartolini and Mair 1990), and the more recently introduced integration-demarcation cleavage (Kriesi 1998; Kriesi et al. 2006). Data from the European Election Survey (2009, 2014) allow the implementation of the novel design in order to study electoral competition in 27 EU member states. For this thesis to empirically address the question of electoral competition in Europe a preliminary, methodological development has to be made. Indices of political polarization are generally produced using survey respondents’ average perceptions of party positions. I show that this approach leads to systematic measurement error: the problem, known as Differential Item Functioning (DIF), depends on the fact that voter perceptions are subjective and cannot be directly compared, neither within nor between countries. To separate the actual polarization from perceptual bias, I develop a two-stage Bayesian Aldrich-McKelvey (2S-BAM) scaling procedure and apply Dalton’s index on DIF-corrected measures of party positions (ideal points) on both dimensions. Results show that when standard DIF-inflated polarization indices are used, left-right ideology seems to be still structuring European electoral competition. However, once the indices are optimized, using party ideal points, the integration-demarcation cleavage gains the upper hand over the left-right dimension in structuring electoral competition in contemporary Europe. Thus, this thesis makes both a methodological and theoretical, as well as an empirical contribution to the literature in this field.