不確定性が急激に高まった年の大統領選挙というのは、歴史的事例では1860, 1932,
1968, 2008などで、此等の事例の共通点は・・・APの記事から

“Crises of varying degrees produce fascinating and often consequential elections:
Think 1860, 1932, 1968, 2008. Such races turn on questions of chaos versus order
and favor the candidate who seems to offer the best chance of bringing order to the
country in times of uncertainty,” presidential historian Jon Meacham said.
“What’s interesting about those examples is that incumbents, or candidates of the
incumbent party, lost all of them.”
https://apnews.com/3441fea7832f3c4a1e45efa87fa2f29e
Analysis: Facing virus outbreak, Trump’s tactics fall short
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＊日本国内の2009年の自民党下野も、この筆者の言うところの共通のパターン