GOP-mandated, in-person voting on April 7 contributed directly and significantly to increases in COVID-19 cases in Wisconsin.

Below I've pasted excerpts from a study conducted by economists from the UW and Ball State. Below them, you'll find a link to the study itself.  

I found data from some relevant counties and created a new spreadsheet and graph, putting a "face" on the statistics these economists used and the conclusions to which they came. You'll find the spreadsheet at the bottom of this page.

Study excerpts: “Our results indicate that Wisconsin counties with higher levels of in-person voting per polling location led to increases in the weekly positive rate of COVID-19 tests. Furthermore, counties with higher absentee voting participation had lower rates of detecting COVID-19 two to three weeks after the election. We show that this finding is unlikely to be a function of differing trajectories by population density, and controls for demographics and measures of social distancing do not explain our findings either.

Due to the political nature of the decision in switching to absentee voting (vote-by-mail), our work relates to an emerging economics literature suggesting that political beliefs and actions may impact the spread of the SARS-CoV-2 virus.

Across all models we see a large increase in COVID-19 cases in the weeks following the election in counties that had more in-person votes per voting location, all else equal. Our results support and extend the Wisconsin Department of Health Services findings on the link between the spread of COVID-19 and in-person voting.

Our results confirm the Wisconsin Department of Health Services findings on the link between the spread of COVID-19 and voting using testing and tracing methods. However, the tracing investigation undertaken was not comprehensive, and our results indicate a much larger potential relationship. Specifically, results show that counties which had more in-person voting per voting location (all else equal) had a higher rate of positive COVID-19 tests than counties with relatively fewer in-person voters. Furthermore, we find a consistent negative relationship between absentee voting and the rate of positive COVID-19 tests. Similar to patterns with in-person voting, this association appears two to three weeks after the election and persists across a number of specification tests, but is not observed in the pre-trend week prior to the election.”

Study link: https://www.nber.org/papers/w27187.pdf