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

• Author: Yimeng Li,Michelle Hyun,R. Michael Alvarez
• DOI: http://doi.org/10.1177/10659129211033340
• Published date: 01 September 2022
• Date: 01 September 2022
• Subject Matter: Articles

https://doi.org/10.1177/10659129211033340

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DOI: 10.1177/10659129211033340

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Introduction

On Election Night, November 6, 2018, Republican candi-

date Young Kim thought she had won California’s thirty-

ninth U.S. House election. She had a lead of 3 percentage

points over her Democratic opponent Gil Cisneros with

more than 150,000 votes counted. But weeks after

Election Day, once all of the ballots in the thirty-ninth

congressional race from Orange, Los Angeles, and San

Bernardino counties were verified and tabulated, Kim

learned that the outcome had flipped parties and that

Cisneros was the winner.

Young Kim is not the first candidate to assume that the

reported election results on Election Night (or those

reported early in the morning of the day after the election)

are an accurate indication of the final outcome of the race.

She is also not alone in witnessing that the vote shares,

and even the House seats, slipped away during days after

the election. Nationwide, in the U.S. House elections in

2018, vote shares shifted toward Democratic candidates

in 156 congressional districts—with a magnitude of 2

percent or more in sixty-three districts—and toward

Republican candidates in just thirty-four seats, as shown

in Figure 1.1 Six Democratic candidates ultimately won

while trailing the morning after Election Day (five out of

thirty toss-up seats labeled by the New York Times on a

5-point competitiveness scale), and three more barely lost

(by less than 0.1%) after shifts in the vote shares in their

favor. As increasing numbers of ballots are tabulated in

many jurisdictions, the vote margins in recent elections

are often observed to shift toward favoring Democratic

candidates, which researchers have called the “Blue

Shift” (Foley and Stewart 2020).

Candidates, like Young Kim, and their supporters may

wonder how an election can flip from one party’s can-

didate to another party’s candidate if not for voter fraud.

Young Kim, and Mimi Walters in California’s 45th

congressional district race in Orange County—another

candidate witnessing the vote share shifting toward her

Democratic opponent—both alleged voter fraud is behind

the vote share shifts.2 Walters told supporters in an email

that she needed donations to stop Democrats “from over-

turning the will of the voters.” Kim, meanwhile, said that

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33340PRQXXX10.1177/10659129211033340Political Research QuarterlyLi et al.

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1California Institute of Technology, Pasadena, USA

Corresponding Author:

Yimeng Li, Division of the Humanities and Social Sciences, California

Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125,

USA.

Email: yimeng.li@caltech.edu

Why Do Election Results Change after

Election Day? The “Blue Shift”

in California Elections

Yimeng Li1, Michelle Hyun1, and R. Michael Alvarez1

Abstract

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.

Keywords

American elections, “Blue Shift”, voting by mail

2022, Vol. 75(3) 860–874

Article