ATLANTA — One month before the Nov. 8 midterm elections, several of Georgia’s grass-roots organizing groups huddled to plan for what they saw as an inevitable outcome: another Senate runoff.
This plan, formulated by the same organizers who helped elect the Democratic senators Raphael Warnock and Jon Ossoff, included budgeting for an added month of canvassing and door knocking, increasing staff outside of the Atlanta area and recording robocalls that could start reaching voters the day after Election Day.
Halfway into Georgia’s four-week runoff period, that plan is now in full swing. And grass-roots organizers are not alone. Georgia Democrats and Republicans have poured a combined $38 million into television ads, hired more than 700 additional field staffers and extended invitations to governors, senators and at least one former president ahead of Election Day on Dec. 6.
Campaigns and allied groups are feverishly knocking on doors, waving signs and sending text messages imploring Georgians to head back to the polls for the second time in less than a month. All the while, Mr. Warnock and his Republican opponent, Herschel Walker, are traveling alongside high-profile surrogates to re-energize supporters.
“If you want to be on top of your game in Georgia, you plan for runoffs,” said Hillary Holley, executive director of Care in Action, the political arm of the National Domestic Workers Alliance, who helped do just that before the general election.
Yet, all of this activity is facing some new hurdles: A 2021 law shortened the window for campaigning, giving candidates just four weeks — including the Thanksgiving holiday — to make their final appeals to weary voters. And the stakes, along with national attention, diminished significantly when the Democrats clinched control of the Senate earlier this month, downgrading the race from a final battle over control of the chamber to a fight over whether Democrats would win a 51st vote.
That reality may have hit Republicans hardest. Mr. Walker’s troubled campaign must not only convince his voters to return but also try to persuade those who rejected him in November to change their minds.
Democrats’ biggest challenge is fighting complacency, by finding a message that excites their base and at the same time appeals to voters who don’t often support the party.
Georgia Senate Runoff: What to Know
Both parties are framing the race in the direst terms. Democrats have portrayed it as a chance to expand their Senate majority, claim more seats on committees and confirm like-minded federal judges. Republicans are describing Mr. Walker as a key part of a Republican firewall against President Biden’s legislative agenda.
“It’s not just about this December,” Gov. Brian Kemp, a Republican, said at a campaign rally in the Atlanta suburb of Smyrna last week, his first appearance alongside Mr. Walker since winning re-election. “It’s going to be about November two years from now and the future of our country.”
Mr. Kemp bluntly cast the Senate runoff as a “turnout election,” asking Republican voters: “Who’s more motivated? Is it us or them?”
Just how motivated G.O.P. voters are is not yet clear. While die-hard conservatives are likely to vote in large numbers to support Mr. Walker, he will also need to increase support among moderate and independent voters in the Atlanta suburbs. During the general election, more than 200,000 Republicans cast ballots for Mr. Kemp but not for Mr. Walker.
And Mr. Walker has continued to face damaging headlines. On Tuesday, a woman who has not identified herself held a news conference to further detail her claim that Mr. Walker pressured her to have an abortion in the early 1990s. Mr. Walker has denied the account.
On Wednesday, CNN first reported that Mr. Walker had claimed a tax exemption on his home in Texas, describing it as his primary residence on his 2022 property taxes, even as he ran for office in Georgia. His campaign did not respond to requests for comment.
The Walker campaign has held more events in metro Atlanta in recent weeks and is leaning on surrogates like Mr. Kemp to bolster his candidacy. The governor turned over his data and field workers to Mr. Walker’s team the day after the general election. The Senate Leadership Fund, the committee backed by Senate Republican Leader Mitch McConnell of Kentucky, has provided $2 million for Mr. Walker’s turnout operation — the committee’s first investment in a get-out-the-vote program — on top of more than $14 million it has spent on ads supporting Mr. Walker.
In addition, the state G.O.P., Republican National Committee and National Republican Senatorial Committee have contributed voter data, money and personnel to Mr. Walker’s campaign.
“Governor Kemp wrote the playbook for how to win big in Georgia,” Steven Law, the president of the Senate Leadership Fund, said in a statement. “As we learned in 2020, Republican turnout is essential for victory in a runoff election, and we are leaving no stone unturned.”
Republicans are trying to avoid a repeat of their losses in the two Senate runoffs in Georgia in 2020, when many rank-and-file conservatives, who distrusted the outcome of the presidential election, chose not to vote at all. State and grass-roots leaders in the party now say they are spending more time making sure that Republican voters turn out again than trying to persuade independents to support Mr. Walker.
“I think we’ve kind of worked through that,” Sammy Baker, chairman of the Gwinnett County Republican Party, said of the election denialism that took root among many in his party two years ago. “And, you know, more people understand, if they don’t show up, we just won’t win.”
Former President Donald J. Trump has not yet indicated whether he will hold a rally in Georgia before the runoff. But a number of Republican operatives and activists have said they prefer he stay away.
Mr. Warnock, for his part, is working to turn out the same coalition of voters that helped him win 37,600 more votes than Mr. Walker on Nov. 8. (He won 49.5 percent of the total vote, however, and Georgia law forces a runoff if no candidate reaches 50 percent.)
That Democratic coalition includes voters of color, voters under 30 and people who have voted only infrequently, particularly in central and South Georgia.
Mr. Warnock also aims to build on his support from voters who split their tickets. His campaign has begun running a television ad featuring a woman who calls herself a lifelong Republican and says she is “proud to support Brian Kemp” in 2022. But, she adds, “at the end of the day I have to vote for someone that I can trust and that has integrity. And I don’t believe that is Herschel Walker.”
Both candidates have accelerated their fund-raising in the run-up to the runoff, according to federal campaign-finance filings: Mr. Warnock raised $52 million in the weeks between Oct. 20 and Nov. 16 while Mr. Walker raised $21 million.
Mr. Warnock, who has raised more than $120 million for his re-election, has used that enormous fund-raising haul to target as many voters as possible statewide. A week after the general election his campaign announced that it had hired 300 new field staffers across the state. This week, his campaign said it had begun rolling out $1 million in advertising on billboards, posters, online pop-ups and banners pulled by airplanes encouraging voters to head to the polls.
Mr. Warnock is also bringing in celebrities. The Dave Matthews Band will hold a concert for Mr. Warnock in Cobb County, and former President Barack Obama will visit the state next week.
Part of Democrats’ turnout strategy has been fighting for more opportunities to vote. Mr. Warnock’s campaign, the state Democratic Party and Democratic Senatorial Campaign Committee sued to allow voting on Saturday, two days after Thanksgiving. The groups argued that a law that prohibits voting on the weekend after a holiday did not apply to runoffs. A Fulton County judge agreed and rejected Republicans’ appeals.
On Saturday, Fulton County, the state’s most populous county and a Democratic bastion, will begin early voting at two dozen locations with extended hours.
On Tuesday, Douglas County, which sits 20 miles west of Atlanta, became the first county in Georgia to open its precincts for early voting. Ingrid Landis-Davis, chairwoman of the county’s Democratic Party, said she and other volunteers had been conducting “a 24-seven operation,” gesturing to empty coffee pots strewn across the party’s office. She cited lines at a few voting sites as a sign of early enthusiasm in the area.
Ms. Landis-Davis said she and scores of other volunteers have knocked on doors across the county, waved signs and made phone calls at all hours to get voters back out and to enlist more volunteers.
“This didn’t just start three weeks ago,” she said. “What we’re doing is just messaging out: Come back out. One more time. Come back out.”