How has political polarization between Democrats and Republicans evolved over the past decade?
Executive summary
Over the past decade political polarization between Democrats and Republicans has intensified in some dimensions—especially among political elites and in congressional voting—while public-level trends are more mixed, with growing affective divides but uneven change across specific issues and age groups [1] [2] [3]. Scholars point to structural changes in candidate selection, party realignment, and identity sorting as central drivers, even as evidence about the causal role of media or the internet remains contested [1] [4] [5].
1. A decade of sharper elites, muddier mass trends
Research shows a clear, steady increase in ideological distance among elected officials and the candidate pool—so that whoever wins office today tends to be farther from the center than a decade ago—while changes among average citizens vary by measure and issue [1] [2]. Studies referenced by Carnegie and recent mapping work in Nature Human Behaviour both document that partisan elites and candidates have become more ideologically consistent and polarized over decades, with a marked uptick in elite divergence during the last decade [1] [2]. At the same time, large public-opinion surveys find that partisan gaps have widened on many topics but not uniformly: some moral or social measures show little increase while others, like views on government power and climate, have seen significant partisan widening [3] [6].
2. Structural forces and candidate-driven polarization
Multiple analyses emphasize structural mechanisms—party gatekeeping, primary incentives, and institutional incentives—over a simple story of voters becoming more extreme; county party chairs and other selectors have tended to favor ideologically extreme candidates, skewing the candidate pool long before voters choose [1]. Long-term party realignments tied to race, religion and social issues are repeatedly cited as backdrops that have re-sorted Americans into more ideologically coherent blocs, and that sorting has been intensified by parties discovering which identity cleavages mobilize voters [4] [7].
3. Media, social networks, and contested causality
Popular narratives link social media and partisan outlets to rising polarization, but scholarly assessments remain mixed: some work finds little consistent evidence that increased media choice alone produced mass polarization, while other studies point to partisan media’s role in reducing openness to opposing views among its consumers [8] [4]. Cross-national and longitudinal work cautions against treating the internet as a singular cause—affective polarization trends differ across democracies and by cohort—so media likely interact with preexisting structural and identity dynamics rather than acting as the sole driver [8] [5].
4. Affective polarization, issue variation, and demography
Feelings toward the other party—“affective polarization”—have grown substantially over decades and remain a central feature of the last ten years, with large majorities reporting unfavorable views of partisan opponents and greater willingness among the most politically engaged to act on those feelings [6] [9]. Yet issue-level polling shows variation: Gallup documents that partisan gaps widened dramatically on certain policy areas between 2003 and 2023 but remained flat or mixed on others, and newer multidimensional analyses show sorting has declined since 2010 even as ideological distances persist [3] [2].
5. Institutional consequences and the risk landscape
Rising elite polarization has translated into legislative gridlock and heightened institutional strain—the 118th Congress, for instance, registers as more polarized than prior sessions—and scholars warn that polarization’s democratic costs depend on institutional structure and whether distrust translates into political violence or sustained erosion of norms [10] [1]. Research cited by Carnegie and other centers connects higher affective polarization with democratic stress but emphasizes that the U.S. experience reflects the interaction of affective divides with institutional features and political incentives, not affect alone [1].
6. What this means going forward
The past decade shows polarization consolidating among elites and remaining heterogeneous among the public: the trajectory suggests continued strain on compromise and governance unless incentives within parties and candidate-selection processes change, but precise future paths are uncertain because drivers—identity realignment, institutional incentives, media ecosystems—operate together and scholars disagree about their relative weight [1] [7] [4]. Available evidence does not settle whether polarization will deepen uniformly or ebb in particular domains, only that its effects will continue to be uneven across issues, institutions, and demographic groups [3] [2].