The voter requested that the AJC not publish his name.

The Georgia Secretary of State’s Office has opened an investigation into what state officials said was isolated incident.

“We are confident that machines are not ‘flipping’ voters,” said David B. Dove, the office’s chief of staff and legal counsel. “It appears with this particular machine that the county did not properly conduct logic and accuracy testing on this unit. That test ensures the geographic areas on the unit’s screen corresponds to the underlying ballot format. This testing is required by state law.”

Bryan County Election Supervisor Cindy Reynolds told the AJC that the machine was one of eight in operation for early voting. At least 20 people had previously used the machine that day; no one reported any problems to poll workers but, she said, “I went ahead and took it down just to be sure.”

Merle King, executive director of the state’s Center for Election Systems at Kennesaw State University, said it seemed likely that the issue was related to the machine’s calibration.

Georgia, since 2002, has used what in the industry are called "direct-recording electronic" voting machines, or DREs, known by voters for their touch screens. To accurately collect a voter's intent, the touch screen must be tilted toward the voter at approximately a 45-degree angle. If it is improperly calibrated, King said, it will mark the voter's choice either above or below the intended target area.

In this instance, King said, “it sounds like the voter did the correct thing — they checked the summary screen for correctness before casting the ballot.”

The state has received no reports of similar problems elsewhere. King called the problem “uncommon,” noting that the state has “already had close to 800,000 ballots cast on the DREs (this fall) and this is the first report we have had.”

While use of the machine has been stopped, King said all votes already cast will be tabulated after Election Day polls close Nov. 8.

Many of the more than 27,000 voting machines in Georgia are at least 13 years old, and aging machines are an issue for states across the country. The state, however, regularly tests the machines, and officials said the system was ready for the election this year.

Early voting in Georgia began Oct. 17 and runs through Nov. 4. Turnout is running about 4.5 percent ahead of 2012 for the same time period during the last presidential election four years ago.