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Published August 21, 2021 | Supplemental Material + Accepted Version
Journal Article Open

Why Do Election Results Change after Election Day? The "Blue Shift" in California Elections


The counting of votes in contemporary American elections is usually not completed on Election Night. There has been an increasing tendency for vote shares to shift toward Democratic candidates after Election Day in general elections, in particular, in recent U.S. elections. Leveraging important snapshots of precinct-level election returns and precinct-level demographic and political composition from Orange County, California, we conduct the first full-fledged analysis of the potential drivers of vote share shifts. Using an original large-scale post-election survey and unique snapshots of individual-level administrative records, we also provide the first analysis of the characteristics of voters whose ballots were tallied later versus earlier in the process. Far from being anomalous, our results indicate that the shifts are consistent with underlying precinct voter compositions and the order of precinct and mail ballot processing at the individual level in accordance with election administration practices. We find the same driving forces in North Carolina and Colorado, and discuss the consequences of the "Blue Shift" for public concerns about election integrity as states push policy changes regarding access to voting by mail.

Additional Information

© 2021 University of Utah. First Published July 23, 2021. The authors thank the Orange County Registrar of Voters, Neal Kelley, and the OCROV Operations Manager, Justin Berardino, for providing us with data used in this study. We also thank Daniel Guth and Seo-young Silvia Kim for their work on related projects. The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Funding for this project came from the John Randolph Haynes and Dora Haynes Foundation. Hyun's work was supported by the Caltech Summer Undergraduate Research Fellowship program through the James H. Milovich SURF Fellowship. The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Attached Files

Accepted Version - why-do-election-results-change-after-election-day-the-blue-shift-in-california-elections_v2.pdf

Supplemental Material - sj-pdf-1-prq-10.1177_10659129211033340.pdf



Additional details

August 20, 2023
October 20, 2023