[9] This asymmetry has not always existed; in the 20th century, as recently as the 1996 United States presidential election, Republicans and Democrats were both able to cut their opponents' leads during the canvass period.
Foley conjectured that the 2002 enactment of the Help America Vote Act accelerated the pronounced asymmetry of the blue shift phenomenon, because it required states to allow provisional ballots to be cast.
[9] He later found that the variation in the size of the blue shift is positively associated with the number of provisional ballots and the Democratic partisanship of the state in question.
Republican Steve Cooley was up by several points with Los Angeles and Alameda counties, two of the state's largest, scheduled to report most of their ballots around midnight.
In order to meet evening newscasts, Cooley declared victory at 11 pm, but continuing results from the urban counties led to the race being declared too close to call by most media outlets, and Cooley ultimately losing to Democrat Kamala Harris by 0.7 percentage points.
This was a closely contested race for an open seat in the United States House of Representatives that included portions of Orange, Los Angeles, and San Bernardino counties in Southern California.
[3] A blue shift occurred in other California races as well – Republican House incumbents Jeff Denham, Mimi Walters and David Valadao were all leading on election night, but ended up losing as mail-in ballots skewed heavily in favor of their Democratic challengers.
[16] Another notable example of blue shift was the 2018 United States Senate election in Arizona between Republican Martha McSally and Democrat Kyrsten Sinema.
Trump had openly stated that he opposed USPS funding, specifically to prevent mail-in ballots, due to his fears that it could hurt his chances of re-election.
[25] U.S. data and analytics company Hawkfish predicted that on election night in 2020, U.S. Republican party nominee and presidential incumbent Donald Trump would receive more in-person votes than Joe Biden, his Democratic party nominee and principal challenger, but when absentee, provisional, and mail-in ballots were counted, the election would swing against Trump in a classic "red mirage" or "blue shift" scenario.
[26] Asked about the scenario, Trump campaign communications director Tim Murtaugh told reporters, "The news media should get out of the business of predicting the future.
[40][41][42] It was also the first midterm since 1986 in which either party achieved a net gain of governorships while holding the presidency,[43][38][44] and the first time ever in a disadvantageous position.
[47] A "shift" does not usually feature in news coverage as both in-person and mail-in votes are counted beginning at 18:00 when polling booths close.