ATLANTA (NewsNation Now) — Candidates for one of two U.S. Senate seats still hanging in the balance will face off in a debate Sunday that is drawing strong interest beyond Georgia.

That is because the seat — now held by incumbent Republican Kelly Loeffler and being challenged by Democrat Raphael Warnock — is one of two that will tip control of the Senate to either Republicans or Democrats. Loeffler and Warnock face off Sunday in a debate sponsored by the Atlanta Press Club. Although Warnock has sought additional debates, none have been scheduled yet, meaning this could be the only head-to-head debate between the two candidates.

The other Senate seat still undecided is between Georgia Republican U.S. Sen David Perdue, who has declined to meet Democratic challenger Jon Ossoff in additional debates after the two jousted twice before the general election. Ossoff will get a solo platform Sunday to make his case.

Georgia, long a Republican stronghold — but one with rapidly changing demographics — has the two runoffs scheduled for Jan. 5 to settle which party would control the Senate, prompting a huge wave of money and organizing efforts.

Democrats would need to win both seats to win a majority. If Republicans win one seat, they will retain control and be able to block much of Biden’s legislative agenda. Saturday’s rally is hosted by the Republican National Committee and is expected to have appearances from other notable Republicans.

In both races, a runoff is required under Georgia state law because no candidate reached 50% in November. Perdue fell just short of defeating Ossoff because a Libertarian candidate won a small slice of the vote, while Warnock led Loeffler in a 20-way field in which no candidate came close to 50%.

Loeffler and Perdue rallied Saturday in Valdosta with Trump, who came to the state to support the candidates despite continuing questions over whether Trump’s unproven attacks on Georgia’s presidential balloting will cause some of his Republican supporters to shy away from voting in the runoffs.

The 100-minute rally before thousands of largely maskless supporters came not long after Trump was rebuffed by Georgia’s Republican governor in his astounding call for a special legislative session to give him the state’s electoral votes, even though President-elect Joe Biden won the majority of the vote.

Trump has repeatedly and without evidence asserted widespread fraud in the November election, a claim rejected by state and federal officials.

Kemp, in a tweet, said Trump asked him to order an audit of signatures on absentee ballot envelopes in his state, a step Kemp is not empowered to take because he has no authority to interfere in the electoral process on Trump’s behalf.

At the rally, he took aim at Kemp, saying he could assure him victory “if he knew what the hell he was doing.”

Kemp refuted the claims.

In a tweet, Kemp said: “As I told the President this morning, I’ve publicly called for a signature audit three times (11/20, 11/24, 12/3) to restore confidence in our election process and to ensure that only legal votes are counted in Georgia.”

While the governor does not have the authority to order a signature audit, an audit was initiated by Secretary of State Brad Raffensperger and it triggered a full hand recount that confirmed Biden’s victory in Georgia. The race has been certified for Biden and affirmed by the state’s Republican election officials as a fairly conducted and counted vote, with none of the systemic errors Trump alleges.

Meanwhile, the Biden-Harris team continued their transition efforts, President-elect Biden said Friday he would travel to campaign for his party’s Senate candidates.

The deadline for new voters to register for Georgia’s twin U.S. Senate runoffs is Monday. Voters can register or check their registration status at the Georgia Secretary of State’s website. Voters can also register at their county elections office on Monday.