From the Document: "The more an individual interacts with others, and the longer that interaction, the higher the risk of COVID-19 [coronavirus disease 2019] spread. Elections with only in-person voting on a single day are higher risk for COVID-19 spread because there will be larger crowds and longer wait times. Lower risk election polling settings include those with:  a wide variety of voting options;  longer voting periods (more days and/or more hours);  any other feasible options for reducing the number of voters who congregate indoors in polling locations at the same time. The virus that causes COVID-19, is mostly spread by respiratory droplets released when people talk, cough, or sneeze. It may be possible that a person can get COVID-19 by touching a surface or object that has the virus on it and then touching their own mouth, nose, or possibly their eyes. Personal prevention practices (such as handwashing, staying home when sick) and environmental cleaning and disinfection are important actions election ocials, poll workers, and voters can take to help lower the risk of COVID-19 spread."
Centers for Disease Control and Prevention: https://www.cdc.gov/