Martin was far ahead of DeKalb County CEO Vernon Jones with almost 90 percent of precincts reporting, The Atlanta Journal-Constitution reported. The two men were the top vote-getters in a five-person primary in July.
On the Republican side, Chambliss had no opponent in the primary. The first-term senator defeated U.S. Sen. Max Cleland in 2002, using a controversial ad that linked Cleland, who suffered a crippling injury in Vietnam, with Osama bin Laden.
Chambliss is favored to win in November, given Georgia's tilt towards the Republican Party in recent years.
Jones had campaigned as a conservative Democrat, Congressional Quarterly said. He told Democrats that he voted for President Bush in 2000 and 2004.
Martin ran ahead of Jones in DeKalb County in the Atlanta suburbs and in Atlanta.