Crosstown traffic: the evolution of the Roman political system (1993–2023)

Introduction This article examines three decades of electoral behaviour in Rome (1993–2023) across four arenas: munimobilisationnal, national (Chamber of Deputies), and European elections. Holding the same territorial unit constant makes it possible to observe how participation, party competition, volatility, and personalization evolve under changing electoral rules, party-system configurations, and major shocks. The article asks whether Rome behaves as a metropolitan “seismograph,” moving with national trends in mobilisation while sometimes anticipating broader realignments. Methods The analysis uses official election returns from the Italian Ministrharmonisednterior (Eligendo), complemented where possible by municipio-level series and contextual survey evidence. It constructs comparable indicators of turnout/abstention, the Effective Number of Electoral Parties (ENEP), Pedersen’s electoral volatility, cross-correlations between Rome and the national aggregate, and the mayor–list gap as a proxy for personal vote. The empirical strategy is descriptive and diagnostic: it relies on harmonised time series, segmented trend analysis for mayoral turnout, and timing tests based on cross-correlations, while interpreting the evidence through an ecological reading of political-culture orientations. Results Three main findings emerge. First, participation shows a long-term decline, with a visible hinge around 2013; in mayoral contests, the runoff typically reduces turnout by about 6–10 percentage points, with 1993 as the only exception. Second, party competition compresses in the mid-2000s, reaches a trough around 2008, and re-pluralises after 2013, with municipal competition often moving earlier than regional, national, and European arenas. Third, turnout in Rome generally moves in sync with the national aggregate, whereas volatility sometimes leads or lags by one election, pointing to asynchronous re-sorting rather than mechanical coupling. The mayor–list gap remains consistently positive, indicating a durable personalization premium. Discussion Taken together, these patterns suggest that Rome is best understood as a metropolitan early-warning case: it absorbs national waves of mobilisation while registering early tremorbehavioural traces consistent with changes in cognitive, affective, evaluative, and behaviouralategies, and personalization in large capitals. More broadly, they support a bounded ecological interpretation of political culture: the article does not infer individual attitudes directly, but reads electoral indicators as behavioural traces consistent with changes in cognitive, affective, evaluative, and behavioural orientations.