Republican Sen. Saxby Chambliss enlisted Sarah Palin to rally conservatives while Democratic challenger Jim Martin pushed to activate black voters, as they grappled for advantage in a Tuesday runoff that will shape Democrats' hold on power in Washington.

Palin, the Alaska governor who was John McCain's vice presidential running mate, attended private fundraisers Sunday night followed by rallies across the state Monday. McCain carried the state with 52 percent of the vote on Nov. 4.

Martin planned to campaign with prominent Georgia Democrats, including civil rights icon U.S. Rep. John Lewis, as he sought to rekindle the strong showing by African American voters in the general election that President-elect Barack Obama sparked.

Neither Chambliss or Martin crossed the 50 percent threshold in the general election. That race included a libertarian, Allen Buckley, who drew 3.4 percent. Almost one month after the vote, there has been no end to the mudslinging, with fresh attacks ads flooding the airwaves through Thanksgiving.

This week's runoff is critical because Senate Democrats are just two votes shy of the 60 needed to block Republicans from filibusters, delaying tactics meant to hold up Senate votes. Georgia is one of two unresolved contests. The other is in Minnesota, where a recount is under way in the race between Republican Sen. Norm Coleman and Democrat Al Franken.

The Chambliss campaign is hoping Palin energizes the conservative base in a race that will hinge on turnout.

It will be Palin's first return to the campaign trail since her failed vice presidential bid. She is widely rumored to be interested in a run for president in 2012.

Palin is just the latest political luminary to enter the fray in Georgia's heated runoff contest. It has also drawn McCain and Republican rivals Mike Huckabee, Rudy Giuliani and Mitt Romney, as well as Democrats Al Gore and former President Bill Clinton.