With 16 percent of precincts reporting, Chambliss had 65 percent of the vote to Martin's 35 percent. The early returns came mostly from rural counties where Republicans traditionally wield significant sway in a still-overwhelmingly red state. None of the urban Democratic strongholds had yet reported results an hour after the polls closed.

The hotly contested Georgia runoff between the former University of Georgia fraternity brothers will have a significant effect on the balance of power in Washington. Democrats in the U.S. Senate are just two votes shy of the 60 needed to block Republican filibusters - a key bid for power that would be immensely helpful as a Democrat heads to the White House for the first time in a decade.

Georgia is one of the two unresolved Senate races. In Minnesota, a recount is under way in a tight race between Republican Sen. Norm Coleman and Democrat Al Franken. The ballots must be tallied by Friday but the contest could stretch beyond that with a five-member board gathering beginning Dec. 16 to rule on ballot challenges.

Elections officials reported steady to light turnout since polls opened at 7 a.m., and no problems throughout the day. Polls closed at 7 p.m. A spokesman for Georgia Secretary of State Karen Handel predicted turnout would be between 18 and 20 percent, far less than the 65 percent who voted in last month's general election.

Chambliss and Martin each spent much of the day with family. They were scheduled to attend rallies with supporters after watching early returns.

In midtown Atlanta, about 75 Martin supporters and members of the media mingled over hors d'oeurves and awaited the election results. Chambliss briefly addressed a GOP crowd gathered in Cobb County.

Chambliss' argument that he's needed as a firewall to Democratic dominance in Washington resonated with some voters.

Murray Gottlieb, 54, a caterer in Savannah, said he voted for Chambliss because he doesn't want complete Democratic control of the Senate.

"I support Barack Obama now. I hope he's the best president we've ever had and we get out of the funk we're in, but I don't want to give him that much power," Gottlieb said after casting his ballot at a church in Savannah.

The ailing economy brought architect Glen McClure, 47, out for Martin.

"My motivation is, I'm unemployed as of yesterday," he said at a library-turned-polling place in Atlanta's upscale Buckhead neighborhood.

Chambliss and Martin both fell short of the 50-percent threshold in a three-way general election race with Libertarian candidate Allen Buckley, who drew 3.4 percent of the vote. It's Georgia's first Senate runoff since 1992, when Democratic Sen. Wyche Fowler was upset by Republican Paul Coverdell.

Chambliss, 65, is seeking a second term after winning in 2002 against Democratic Sen. Max Cleland in a campaign that infuriated Democrats. Chambliss ran a TV ad that questioned Cleland's commitment to national security and flashed a photo of Osama bin Laden. Cleland is a triple amputee wounded in the Vietnam War.

Martin, a 63-year-old former state lawmaker from Atlanta, has aligned himself with President-elect Barack Obama's message of change, and has vowed to provide economic relief for the middle class. A onetime agricultural lawyer from Moultrie, Chambliss has promised to be a firewall against a Democratic-dominated Washington getting a "blank check."