“It’s off-year election kind of slow,” Mr. Bride said. He projected about 17 percent of the county’s registered voters would turn out, down from 43 percent in 2016, when both parties had competitive presidential contests.

DuPage County, a Chicago suburb that has had to relocate more than a dozen polling places, said that as of noon local time, about 49,000 votes had been cast, bringing the overall turnout to around 91,000 — about 14 percent of the county’s 614,000 registered voters.

In Florida’s Palm Beach County, hundreds of volunteer poll workers told officials they could not show up on Tuesday, forcing the county to open some locations late and move other ones.

“We have experienced poll worker no-shows causing some of our polling locations to open late,” Wendy Sartory Link, the county supervisor of elections, wrote on Facebook. She added that several polling locations would have to be moved, and encouraged voters to pick up a ballot from any of the county’s four elections offices.

In Miami-Dade County, about 8 percent of the expected 4,800 poll workers did not show up on Tuesday morning, according to Suzy Trutie, spokeswoman for the county elections supervisor. “Given the light election turnout,” she said, “we are confident we are properly staffed to receive voters.”

At a Miami fire station early on Tuesday, Leah Weston, 34, said she wanted to maintain the habit of casting a ballot on Election Day.

“I just enjoy the ritual of it, of going to my polling place,” she said.

She would have voted early over the weekend, but she chose to “anxiety clean” her home instead. She also figured — correctly — that the fire station would be less of a confined space than the indoor early voting sites.