ABSTRACT This article introduces a novel method to map party systems over time, addressing the challenge of assigning comprehensive spatial ideological scores to coalitions, parties, and independents. Combining public opinion polls, manifesto analysis, and expert surveys, this method evaluates fixed and variable standard deviation models to score distinct 4,157 electoral lists from 5,195 district-level elections across 27 elections in 12 Chilean electoral systems. It proposes a synthetic data approach to simulate party positions within political family constraints, producing a high-density region map and a political lineage chart that visualize ideological evolution over time. Robustness checks, including diagnostics with controlled random noise and variance adjustments, confirm the reliability of these results. Key findings reveal an earlier-than-expected trend of fragmentation, a leftward drift among left-leaning parties, and an asymmetrical party system where fragmentation affects the left while polarization intensifies on the right. This study underscores the importance of expanding within-system estimators to enhance reliability and concludes with research questions that the resulting dataset can address. These include constituency-level shifts in ideological positioning, fragmentation linked to specific institutional reforms, and the dynamics of localized polarization within multiparty systems.
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