Sixty percent of voters are projected to vote by mail nationwide during the coronavirus pandemic. Those who study absentee rejection rates estimate that 1 percent to 2 percent of those votes won't count, which could make a difference in battleground states.
"The vote-by-mail ballot rejections are going to be the hanging chads of 2000," said Daniel Smith, a professor of political science at the University of Florida.
The rate of rejection tends to be higher for Black, Hispanic, female and younger voters in the battleground states of Georgia, Nevada, North Carolina, Pennsylvania and Wisconsin.
Experience matters when it comes to counting mail-in ballots, and many have never experienced an election in which a high percentage of votes will arrive by mail. The number of rejected ballots could be larger than the winning candidate's margin of victory.
In all but five states any voter is eligible to receive an absentee ballot, because of changes made in response to Covid-19.
"When you're in a scenario like we are in Michigan ... where so many citizens are going to be voting by mail for the first time, there are going to be mistakes made," Michigan Secretary of State Jocelyn Benson said. "That will lead to potential challenges, in my view, or difficulties in making sure that every valid vote is counted."
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