Revista de Sociologia e Política

Introduction: Economic inequality and political polarization have emerged as central phenomena in contemporary democracies. This article reviews the literature on an influential theory that rising economic inequality drives political polarization. The aim is to assess the robustness and limitations of this theoretical claim through an analysis of 28 empirical studies published between 2006 and 2023. Materials and methods: We conducted a scoping review of empirical articles published in peer-reviewed journals, excluding working papers and theoretical essays. Searches were performed in Google Scholar and Crossref via Publish or Perish, using the terms “inequality,” “polarization,” “political polarization,” and “affective polarization” in English, Portuguese, and Spanish. Twenty-eight studies investigating the empirical relationship between inequality and polarization were selected. All employed quantitative methods, predominantly time-series cross-sectional (TSCS) designs. Results: The literature can be grouped into three main explanatory strands. The Median Voter Party (MVP) theory posits that inequality increases demand for redistribution, radicalizing left-wing parties and provoking a reaction from the right. The Economic Deprivation Theory (EDT) argues that marginalized sectors, resentful of relative income loss, gravitate toward radical right-wing parties. A third perspective suggests a negative relationship, where inequality reduces polarization by suppressing political participation or fragmenting coalitions. Positive associations predominate (approximately 60%), though inconclusive or substantial negative results are non-negligible. Revista de Sociologia e Política, v. 33, e011 Regardless of theoretical orientation, studies consistently identify low-income, marginalized, or less-educated voters as key actors in polarization. The main divergence lies in how these groups respond: mobilizing toward the left (MVP) or toward the radical right (EDT). Research is heavily concentrated in the United States and other affluent democracies (79%), with almost no studies on newer democracies or Latin America. Discussion: The lack of consistency in defining and measuring polarization and inequality makes it difficult to draw robust conclusions. Disaggregated indicators provide greater precision, yet only five studies perform robustness checks. In contrast, aggregated measures such as the Gini coefficient limit the testing of group-specific theories. Theoretically, there is broad agreement on the leading role of marginalized groups in polarization. Economic Deprivation Theory offers the most convincing explanation for the contemporary rise of the far right. Nevertheless, critical gaps remain: (i) the mechanisms guiding marginalized groups toward different political poles are still unclear; (ii) qualitative methods are largely absent; and (iii) research on Latin American democracies is scarce, where these dynamics may operate differently, and studies on affective polarization.