(iPoster) The Polarizing Middle Ground: Independents in Public Opinion Polarization

• In Event: Poster Sessions: Political Methodology & Foreign Policy I – Great Power Competition and Strategic Rivalry
  In Poster Session: Poster Session: Political Methodology

Abstract

Recent discussions on polarization in the American public have primarily focused on partisans, highlighting the partisan gap and interparty affective polarization (Iyengar et al. 2019). Independents remain largely missing from this discussion despite polling data that suggest they may comprise 40-45% of the electorate (Gallup 2026, Pew 2025). Existing literature on Independents has focused on their relationship with partisanship: traditionally, Independents were considered “partisans in hiding” (Keith et al. 1992), while some researchers have classified them with “moderates” who occupy a central position and bridge partisan conflict (Fowler et al. 2022). Recent results suggest that Independents have clear motivations, such as social capital or distrust of the party system, to avoid identifying as partisans (Killian 2012; Klar and Krupnikov 2016; Reilly, Salit, and Ali 2023).

We investigate the role of Independents in shaping American public polarization using three Wasserstein-distance based measures of public opinion. While Independents traditionally occupy the ideological middle ground between partisans, we demonstrate that they are not static buffers of partisan polarization; rather, they are necessary participants who shift in parallel with partisans, though with a muted magnitude.

This paper offers three main contributions. First, we identify limitations in traditional measures of public opinion and develop a set of Wasserstein measures that allows a more precise assessment of bipolarization, partisan gap, and progressivity. Second, we integrate Independents into the existing framework on partisan polarization and sorting. Lastly, we bridge the simplified views of Independents as either static moderates or "hidden partisans" by showing they occupy a distinct ideological space even as they mirror broader polarizing trends.

We first review the limitations of traditional measures of issue polarization, partisan gap, and issue progressivity. We address these deficiencies, we develop three Wasserstein-distance-based measures that improve on these limitations to analyze ANES and GSS time series items. Our first measure, the Wasserstein bipolarization index, quantifies the extent of polarization as the distance from a maximally polarized distribution. This measure successfully captures well-known characteristics of polarization, such as the spread of opinions towards the poles and increased clustering on either side of the median. Furthermore, our partisan gap and progressivity measures account for the geometry of the entire distribution rather than relying on summary statistics, such as the mean or median, that lose critical distributional information.

Using these measures, we revisit the scholarly consensus on public polarization that stronger partisan cues, rooted in an ideological realignment among the elites, have resulted in partisan sorting and an exacerbated partisan gap (Levendusky 2009; Abramowitz and Saunders 2008). This theory is often supported by empirical observations of diverging partisan group differences in ideological or issue positions, but also an unchanged ideological bipolarization in the entire electorate. Here, we argue that the partisan gap should be compared with bipolarization among partisans for a correct assessment of partisan polarization. We show that despite the steady increase in partisan gap, partisan bipolarization shows a limited increase for only a few items, and partisans are not more significantly bipolarized than the overall electorate including Independents. These findings do not challenge the partisan sorting theory but reveal a new fact: though Independents tend to occupy moderate issue positions in-between diverged partisans, they also do not serve a mediating role in dampening partisan polarization.

We next investigate the role that Independents play in bipolarization. A closer comparison of Independents and partisans reveals a pattern of parallel changes in bipolarization across a vast majority of issue items, though the magnitude of polarization among Independents is more muted. Furthermore, this pattern is notable in every item where overall bipolarization increased significantly. These results indicate Independents are necessary contributors to the broader trend of polarization, even if they hold relatively moderate positions compared to partisans.

Ultimately, our findings underscore that Independents are distinct from partisans but are also integrated with the broader polarizing shifts in public opinion. These results suggest that Independents should not be dismissed as a static or secondary group; rather, more individual attention should be given to their unique position in the trajectory of American polarization.

Authors

• Hane Lee, University of Chicago

• Michael Sobel, Columbia University