Although much has changed in American politics during the decades since the path-breaking 1956–1960 ANES panel survey, the stability of party identification during the Obama-Trump era looks very much as it did during the Eisenhower Administration or, for that matter, during the eras encompassing Vietnam, Watergate, Stagflation, the Iran Hostage Crisis, the Reagan Ascendancy, the Iran-Contra Scandal, and the Persian Gulf War (Green and Palmquist, 1994).

During the 2011–2020 period, raw correlations between party identification scores measured in successive waves of panel interviews tend to be quite high by comparison to most political attitudes. They are higher still when corrections are made for measurement error. Whether these corrections derive from instrumental variables regression or down-to-earth approaches such as index creation, disattenuated correlations imply that party identification changes at a glacial pace.

The same picture emerges from other ways of describing partisan change statistically. Individual-level response variation is relatively rare across panel waves, a pattern affirmed by other recent studies of multi-wave panel studies, most notably Tucker et al. (2019), who analyze twenty-waves of the TAPS panel from 2011 to 2016. They find that shocks at the individual level dissipate quickly; a shock that moves party identification 0.21 scale points in one wave has an effect of just 0.04 scale points 4 months later and just 0.01 eight months later. When we track individual-level partisan trajectories using all three panel datasets, we too find that a small portion of the public experiences durable change, even in turbulent political times. Nor do we see evidence of aggregate party change, whether we track panel respondents over time or examine independent cross-sectional surveys conducted by the Gallup Poll.

Looking back at the dominant theoretical perspectives that are used to explain change or stability in party identification, it seems that our results underscore the importance of deepening social divides. Our initial hypothesis was two-sided in the sense that the stabilizing effects of growing affective polarization and residential segregation could have been overshadowed by the destabilizing effects of changing party issue positions, the emergence of new issues that divide the parties, and new communication technologies that accentuate those divisions. The fact that party identification seems at least as stable now as it did when the parties were less ideologically distinctive and mercurial vindicates a central argument in Campbell et al. (1960), namely, that party attachment is not primarily driven by ideological affinity. We are quick to concede, however, that this conclusion is not rooted in a direct test of individual-level responsiveness to perceived party stances, a test that presents a host of methodological challenges when using non-experimental panel surveys (Lenz, 2012; Green and Palmquist, 1990).

Although stability over time remains a key feature of American party attachments, we conclude by calling attention to the crucial distinction between slow change and none at all. For those who study elections using cross-sectional survey data, the results presented here are reassuring insofar as they suggest that the pace at which partisanship changes is too slow to be consequential during a given election season. At the same time, the caricature of party identification as an “unmoved mover” creates a host of empirical anomalies that become apparent when researchers track partisan attachments over decades and find substantively large and sustained movements (cf. Kollman and Jackson 2021, Chapter 4). To be empirically sustainable, theoretical accounts must explain why party attachments resist change as well as why meaningful changes do occur over voters’ lifetimes.