So far this year, Republicans are well behind Democrats in applying for mail ballots, several experts said.

“There is a very clear trend in many key states in which Democrats — either registered Democrats or voters that political pros model as Democratic voters — are requesting mail-in ballots at a significantly higher clip than Republicans,” said Kyle Kondik, the managing editor of Sabato’s Crystal Ball at the University of Virginia Center for Politics.

A running tally by J. Michael Bitzer, a professor of political science at Catawba College in North Carolina, found that Democrats in the state had requested nearly three times as many absentee ballots as Republicans.

As of Sept. 17, according to his analysis, 889,000 ballots had been requested; of those, 448,000 requests were from registered Democrats and 154,000 from registered Republicans. (The rest were either unaffiliated voters or members of other parties.)