The Cobb County elections office, which drew fire from voting rights groups when it closed more than half of its early-voting sites for the upcoming Senate runoffs, has tweaked its plans but will still have fewer locations for residents to cast ballots in advance.

Cobb, the third-most-populous county in the state, with more than 537,000 registered voters, had reduced its early-voting sites from 11 in the November general election to five for the Jan. 5 runoffs, which have captured national attention because the outcome could decide control of the U.S. Senate.

The NAACP Legal Defense and Educational Fund sent a letter to elections officials protesting the plan to shutter three of the four sites in the southern part of the county, which has the highest concentration of Black and Latino voters.

The new plan would relocate one polling place to a recreation center in the southern part of the county and add two locations during the final week of early voting.

Janine Eveler, elections director for the county, said she scaled back the early-voting sites because she did not have adequate staffing. She said she started this election cycle with fewer seasonal workers, because some were afraid to work because of the pandemic. Eveler said workers were exhausted after the intense general election, which featured hours-long lines amid increased voter turnout and glitches with a new voting system, as well as two recounts as President Trump and his supporters protested his loss to Democrat Joe Biden.

“Between covid, the workload and the holidays, we have simply run out of people,” Eveler said. “Many workers told us they spent three weeks working 14- or 15-hour days, and they will not do that again. We simply don’t have time to bring in and train up more workers to staff the number of locations we had for November.”

Sens. David Perdue and Kelly Loeffler, the state’s Republican incumbents, are defending their seats against Democrats Jon Ossoff and Raphael Warnock. The runoff became necessary because neither Perdue, who is seeking a second term, nor Loeffler, who is running to complete the term of former senator Johnny Isakson (R), got more than 50 percent of the vote in last month’s general election.

Although officials expect fewer than the 5 million voters who cast ballots in the general election, turnout could be more robust than in previous runoffs, because of the stakes. If the incumbents win, Republicans will retain control of the Senate; if the Democrats win, they will control the chamber, with Vice President Kamala D. Harris as the tiebreaker.