The gap between stated voting support for Mr. Trump and Joseph R. Biden Jr. grows by about 2.5 percentage points in Mr. Biden’s favor when a county has extremely high levels of coronavirus-related deaths relative to when it has low levels. These changes may come within counties as the number of virus-related deaths change, or across counties at any given point in time. For example, Covid-19 fatalities exploded in Wayne County in Michigan in April, suggesting a 1.25-point expansion of the gap between Mr. Trump and Mr. Biden, which could grow larger if deaths there continue to increase.
Cases in Maricopa County, in Arizona, have nearly quadrupled in the last two months, suggesting an 0.6-point increase in the vote support gap between the candidates. Other places have seen little impact from Covid-19, such as Wyoming and some Plains states. Our data show that Mr. Trump has continued to do well in those states, perhaps even increasing his share of the vote in recent months.
Republicans running for the U.S. House and Senate lose just as much support as Mr. Trump does when deaths rise locally. It may feel as if all politics is national, but it is not.
Research shows that when people are killed in action during wartime, residents of the place the victims are from tend to hold elected leaders in Congress and the White House accountable. Political scientists have found this to be true for midterm and presidential elections during the Civil War, the Vietnam War, and the wars in Iraq and Afghanistan. Coronavirus-related deaths seem to be having a similar effect.
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https://www.nytimes.com/2020/07/28/upshot/polling-trump-virus-election.html
