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Of Time and the Development of Partisan Polarization


  • Financial support for the most recent data collection utilized here came from the National Science Foundation, Grant SBR-9601295. We thank Stephen Weatherford and Eric Smith for their comments. We are also grateful for the technical assistance of Kuang-hui Chen and the financial support provided by the Academic Senate of the University of California, Santa Barbara and the Institute for Governmental Studies at the University of California, Berkeley.

Laura Stoker is associate professor of political science, University of California, Berkeley, 210 Barrows Hall, Berkeley, CA 94720-1950 ( M. Kent Jennings is professor emeritus, University of Michigan and professor of political science, University of California, Santa Barbara, 3834 Ellison Hall, Santa Barbara, CA 93106-9420 (


In this article we address the topic of increasing partisan polarization in the American mass public, focusing on the twin influences of individual-level development and cohort replacement and the interaction between the two. We posit a model of individual development that consists of declining openness to change beyond young adulthood, an increase in party-issue constraint as age advances, and cohort-specific responsiveness to changes in the partisan environment. Results from a long-term panel study provide initial evidence of these dynamics. We then use simulations to generate expectations about how these developmental processes play out across cohorts, issues, and time. These expectations are evaluated through a cohort analysis of National Election Studies data from 1972 to 2004. Overall, our results provide a new perspective on the dynamics of individual political development and their implications for the timing, extent, and future trajectory of partisan polarization in the U.S. electorate.