Despite the trend toward homogenization of the political space, which serves as characteristic of modern nation-states, cross-regional differences persist, and sometimes even intensify. For that reason, the question arises why some regions almost do not deviate from national political trends, while in others a specific electoral landscape, special party systems, regionalist parties develop. Explaining these differences, researchers, as a rule, rely on social-economic, cultural, geographical and historical features of the regions. At the same time, large-N comparative studies require the quantitative measurement of cross-regional differences, and it is most problematic to find indicators that reflect the historical specificity of the regions. In the article, based on a tool developed for the comparative analysis of Western European regions, an original scale is proposed for quantitative measurement of the uniqueness of the history of Russian regions - the index of the specifics of political history (ISPI). This instrument is tested on the empirical material of such manifestations of the heterogeneity of the Russian political space as the intensity of regionalism in the early 1990s and the heterogeneity of the party-electoral landscape in 2000s. The analysis finds that history matters, and the proposed index is a promising tool for cross-regional comparative studies.