COVID-19 and Other Election Emergencies: Frequently Asked Questions and Recent Policy Developments [July 16, 2020] [open pdf - 1MB]
From the Summary: "This report addresses frequently asked questions and policy developments surrounding 'election emergencies'. For the purposes of this report, election emergencies are defined as unexpected, rapidly developing, external events that could substantially interrupt normal voting, election administration, or campaigning. Examples include sustained natural disasters, major disease outbreaks, or certain attacks on election systems. There appears to be no modern precedent for a nationwide emergency in the United States, such as COVID-19 [coronavirus disease 2019], affecting elections and voting. Election administrators do, however, routinely prepare for various contingencies. Prominent examples of recent election emergencies in the states include the 2001 terrorist attacks; Hurricanes Katrina and Rita in 2005-2006; and an H1N1 (swine flu) pandemic in 2009. Effects from each episode varied substantially."
CRS Report for Congress, R46455
Congressional Research Service: https://crsreports.congress.gov/