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

AuthorYimeng Li,Michelle Hyun,R. Michael Alvarez
Published date01 September 2022
Date01 September 2022
Subject MatterArticles
Political Research Quarterly
© 2021 University of Utah
Article reuse guidelines:
DOI: 10.1177/10659129211033340
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
33340PRQXXX10.1177/10659129211033340Political Research QuarterlyLi et al.
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,
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
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.
American elections, “Blue Shift”, voting by mail
2022, Vol. 75(3) 860–874

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