COVID-19 cases and employee unavailability are behind the significant slowdowns in ballot delivery happening in parts of Michigan and Pennsylvania, the U.S. Postal Service told a federal court this weekend.

Agency data shows that a significant share of absentee ballots in Detroit, greater Michigan, and central Pennsylvania all regions that could play a crucial role in deciding the presidential election are not arriving within an on time window of about two days. On Saturday in the greater Michigan district, the percentage of ballots delivered on time was 69.1%. It was 78% in the Detroit district, and 56.6% in central Pennsylvania.

Hundreds of USPS employees in Detroit facilities have tested positive for COVID-19 since the start of the pandemic. A disproportionate number of postal workers in Detroit are still contracting the coronavirus or missing work for family obligations or because family members have the virus, a postal official testified Saturday. The same is true for facilities in central Pennsylvania.

Were reacting to it, making the necessary adjustments, Dane Coleman, the regional vice president of processing operations for the eastern U.S., said. Plants in central Pennsylvania and Detroit are sending some of their non-election mail to other facilities for sorting help, and the agency is reassigning nearby employees to cover staffing shortfalls, Coleman said. But we do know and acknowledge that weve had some impacts because of that, he added.

If too many absentee ballots arrive late to election officials, it could easily tip the outcome of the race. Supporters of former Vice President Joe Biden are far more likely than supporters of President Donald Trump to have relied on the mail to cast their votes.

Note: If you have not voted by this point, you should drop off your absentee ballot at an authorized location instead of relying on the mail, or you should plan to vote in person.