You may recall the controversy surrounding the vote back on April 7th in Wisconsin. The governor had attempted to change the voting to be conducted entirely by mail but was overruled by the Supreme Court. Now it appears that as many as 52 people were infected with COVID-19 as a result of voting in person.
A contact tracing analysis has laid out how this happened in a really interesting (and technical) white paper here.
One point in the paper that is probably fairly obvious but worth calling out is the counties with fewer polling locations had higher density voters and those counties ended up seeing more cases 2-3 weeks after polling closed. See this thread from Dr. Eric Feigl-Ding for more information.
You can see in this graph number of visits to points of interest (POI) spiked on the date of election. This means more contact. More contact = more opportunity to spread the virus.