FiveThirtyEight: “As many states have changed their laws to encourage the use of mail voting during the pandemic, one big problem has become apparent: the number of mail ballots that are rejected. Rejected absentee ballots, most of which are cast by mail, have long been an issue, but a manageable one. According to the Election Administration and Voting Survey, less than 1 percent of the 33.4 million absentee ballots submitted in the 2016 general election across the 50 states and Washington, D.C., were rejected.1 This year, though, rejection rates could be much higher because so many people are voting by mail for the first time and may not know the rules. According to research by David Cottrell, Michael C. Herron and Daniel A. Smith, voters without experience voting by mail are up to three times more likely to have their ballots rejected.”

“And even if the absentee-ballot rejection rate turns out to be as low as 2016’s, there will simply be a lot more absentee voting this year, and 1 percent of a big number is still pretty big. According to an analysis by NPR, more than 550,000 absentee ballots were returned but not counted in this year’s presidential primaries — and that number is almost certainly an undercount, considering that data was available in only 30 states. At the very least, that far outstrips the 318,709 absentee ballots that were rejected across the 50 states and Washington, D.C., in the much higher-turnout 2016 general election.”