TRUMBULL — The demand for absentee voting is keeping Town Clerk Mary Markham and her staff busy. Inside the records vault, the staff has sorted boxes of returned ballots — more than 3,500 so far —while another section is dedicated to tracking ballot applications and the associated blank ballots to be sent out.

“There’s more downstairs,” Markham said as she and Assistant Town Clerk Susan Cole prepare to sort through another mailing crate full of envelopes that has just arrived.

In the hallway, three residents are filling out their ballots at a table set up near the registrar’s office while six more people have dropped off their absentee applications in person and are waiting to receive their ballots. Outside, a steady stream of people are using the ballot drop box to cast their votes without relying on the U.S. Postal Service.

And there are still two weeks to go until Election Day.

“Normally, Trumbull will have a few hundred people vote by absentee ballot,” Democratic Registrar Jean Rabinow said.

This year, she estimated as many as 7,000 residents, about one in four registered voters, could vote absentee.

“Connecticut doesn’t really have a tradition of large numbers of people voting by mail, because of the restrictions on the acceptable reasons for voting absentee,” she said.

But this year, with COVID-19 being an acceptable reason, demand for absentee ballots was expected to surge.

And it has, she said.

The explosion in absentee voting is raising some concern because the process of voting by mail carries a somewhat greater chance of human error.

“You have to fill the ballot out correctly, place the ballot into the inner envelope, sign the inner envelope and seal it inside the outer envelope,” Rabinow said.

Once the ballot arrives, the town clerk’s office must stamp the received ballot and maintain a continual chain of custody until the ballot is counted on Election Day. Failure to follow any of these rules could get a ballot disqualified.

In addition, a person who makes a mistake on the ballot while voting in person would likely have a chance to correct the error before leaving the polling place, Rabinow said.

“For example, if someone double votes (votes for more than one candidate in a race), the machine would reject the ballot when they placed it into the scanner,” she said. “Once they know they made a mistake, they could request a new ballot.”

When the town clerk receives an absentee ballot, workers make a notation on the voter rolls that the person has cast an absentee ballot. If the person were to show up at the polls on Election Day, their name would have an “A” next to it and poll workers would inform them that they already voted.

If a person shows up at the polls and tries to drop off their absentee ballot, the individual would be directed to cast an in-person vote, and the absentee ballot would be destroyed. Finally, should a person hand deliver the absentee ballot to the town clerk on Election Day, officials would verify the ballot, then immediately contact the polling location to inform the workers that the person has voted by absentee ballot.

First Selectman Vicki Tesoro acknowledged the slightly greater risk of an absentee ballot being disqualified, but said she was confident in the safeguards in place for voting.

“Just follow the instructions, it’s as simple as that,” she said.

Tesoro also reminded voters that even if they have requested and received an absentee ballot, they could still change their mind and vote in person on Election Day, as long as they have not already sent in their ballots.

Republican Registrar William Holden could not be reached for comment.