By Rachel Kapochunas, CQ Staff

With a Dec. 2 runoff date for their Georgia Senate race looming just three weeks away, Republican incumbent Saxby Chambliss and Democratic challenger Jim Martin have had to continue campaigning full steam ahead — even though Georgia’s election officials haven’t yet certified that Chambliss has fallen just short of the majority vote he needed to win the Nov. 4 general election outright.

Chambliss on Monday remained just below the majority vote threshold needed to avoid a runoff. He had 49.8 percent of the vote with 99 percent of precincts reporting, to 46.8 percent for Martin, a former state representative who ran unsuccessfully for lieutenant governor in 2006. Libertarian Allen Buckley received the remaining 3.4 percent. Georgia’s Secretary of State office plans to certify the Senate race results this week, after the vote count is completed.

Both candidates have moved quickly to try to line up high-profile party support for the runoff campaign. Arizona Sen. John McCain — who carried Georgia as the Republican presidential nominee but lost the national election to Democrat Barack Obama — has committed to attend a rally and fundraiser for GOP Senate colleague Chambliss on Thursday. Chambliss spokeswoman Michelle Grasso said discussions also are under way with GOP vice presidential nominee Sarah Palin , the governor of Alaska, as well as three well-known Republicans who rallied behind McCain after losing to him earlier this year in the contest for the party’s presidential nomination: Mike Huckabee, a former governor of Arkansas; Rudolph Giuliani, a former New York City mayor; and Mitt Romney, a former Massachusetts Governor.

Martin’s campaign, meanwhile, has been in contact with Obama’s staff, but has no firm commitment from the president-elect, according to Martin campaign communications director Matt Canter on Monday. “There are no plans at this time to come to the state, but the request has been made,” Canter said. Canter added that Obama’s campaign team is already lending expertise and experienced campaign staffers to Martin. While President Bush trounced Democrat John Kerry in conservative-leaning Georgia by 17 percentage points in 2004, Obama trimmed McCain’s winning margin in the state to 5 points.

State analysts say the race will test whether Democratic campaign strategists can mobilize Obama supporters to go to the polls without Obama on the ticket. Martin’s first ad of the runoff campaign prominently features Obama and aligns Martin with the president-elect. “Jim Martin will work with Barack Obama to get our economy moving again,” a voiceover states in the ad.

And Martin can make a stronger argument than he could before Nov. 4 that he would have more clout than Chambliss in a Senate dominated by the Democrats. The Democrats’ predicted gains, still speculative before Election Day, are now tangible at six seats, with the races for Republican seats in Georgia, Minnesota and Alaska still undecided. That means the Democrats, who entered the elections with effective control over just 51 of 100 seats, already have clinched 57 seats in the upcoming 111th Congress, counting two Independents who have caucused with Democrats.

Factors that are nearly impossible to predict will play major roles in deciding the outcome of a runoff that now appears likely. Chambliss would need to add on a much smaller percentage to win a one-on-one contest with Martin, but Democrats can place their hopes that the well-known incumbent already tapped all the support he is going to receive. While Chambliss’ views on issues may more closely align with those of some of the state’s Libertarians, both candidates will court support from the small but potential decisive group of voters who favored Buckley.

Turnout is likely to be much lower for the runoff than for the Nov. 4 election: Democrats have to limit the dropoff among their party’s large African-American constituency, which turned out in huge numbers behind Obama’s bid to become the nation’s first black president, while Republicans need to motivate a base of voters discouraged by the party’s loss of the White House and major setbacks in both chambers of Congress.

The Democratic Senatorial Campaign Committee — a fundraising juggernaut that invested $5.5 million in independent expenditures in Georgia’s Senate general election campaign — is likely to make a major effort behind Martin in the runoff, and it is appears unlikely that its cash-strapped partisan counterpart, the National Republican Senatorial Committee, will be able to make a comparable effort on behalf of Chambliss.

Chambliss’ campaign said its focus has been on setting up campaign events and raising money. “It’s going to be a very, very expensive runoff,” Grasso said. “We already know that the Democrats plan to pour millions of dollars into Georgia to try to unseat the senator and we have to be prepared.”

Grasso said Chambliss will begin airing new television ads this week.

Chambliss has received some backup from the conservative group Freedom’s Watch, which is running a television commercial in Georgia that also hits out at Martin on taxes. The commercial asks whether it was Martin’s “evil twin” or Martin himself who supported past tax increases in the state.

Issues involving the nation’s struggling economy were especially influential in this election, according to state political experts such as Charles S. Bullock III at the University of Georgia. For most of the campaign, polls showed Chambliss likely to easily win the general election, but those numbers tightened considerably after Chambliss voted in support of the financial industry assistance legislation, enacted in early October, that was widely branded the Wall Street “bailout” bill.