Are party families in Europe ideologically coherent today?

Researchers classify political parties into families by their shared cleavage origins. However, as parties have drifted from the original ideological commitments, it is unclear to what extent party families today can function as effective heuristics for shared positions. We propose an alternative way of classifying parties based solely on their ideological positions as one solution to this challenge. We use model-based clustering to recast common subjective decisions involved in the process of creating party groups as problems of model selection, thus, providing non-subjective criteria to define ideological clusters. By comparing canonical families to our ideological clusters, we show that while party families on the right are often too similar to justify categorizing them into different clusters, left-wing families are weakly internally cohesive. Moreover, we identify two clusters predominantly composed of parties in Eastern Europe, questioning the degree to which categories originally designed to describe Western Europe can generalize to other regions.