ATLANTA (BLOOMBERG) - Both of Georgia's Senate races are going to runoffs, leaving control of the Senate in limbo until January.

Incumbent Republican Senator David Perdue was just shy of the 50 per cent vote threshold needed to claim the seat outright, with most of the ballots counted. He will now once again face off against Democrat Jon Ossoff, who trailed as of Friday (Nov 6) by about 98,000 votes out of about 4.9 million cast on Tuesday.

Libertarian candidate Shane Hazel drew 2.3 pre cent of the vote, but only Mr Perdue and Mr Ossoff will be on the ballot in January.

Mr Perdue's campaign manager Ben Fry said his candidate got the most votes in this election and would do so again in the runoff.

"A vote for Jon Ossoff is a vote to hand power to Chuck Schumer and the radical Democrats in Washington," Mr Fry said in a statement Friday. "Georgians won't let that happen."

Mr Ossoff said the state's changing demographics will carry him through in the head-to-head contest on Jan 5.

"Change has come to Georgia," Mr Ossoff said at a news conference Friday morning. "This is a different state. Georgia has become younger and more diverse every day of the last decade."

With Georgia's other Republican senator, Ms Kelly Loeffler, already headed to a Jan 5 rematch against Democrat Raphael Warnock, Democrats still have a narrow, if unlikely, path to win control of the Senate by winning both Georgia seats.

That sets up an epic national battle over the state as outside groups and both parties pour money and other resources into swaying the vote.

It also would prolong partisan rancor over the Senate races, alongside potential legal fights in the presidential contest between President Donald Trump and Democrat Joe Biden.

The Senate totals from Tuesday's election now stand at 48 Republicans to 48 senators who align with Democrats. In addition to the two Georgia races, Republican incumbents in North Carolina and Alaska are leading as the final votes are counted.

If Mr Biden wins the presidency and Democrats win both of Georgia's runoffs, the tie-breaking vote in the Senate would be held by Mrs Kamala Harris, as vice-president. This would give Democrats full control of government - albeit by the slimmest of margins - since they also managed to hang on to control of the House.

The state also is in play in the presidential race.

As votes continued to be tallied Friday, Mr Biden took the lead from Mr Trump by a narrow margin of less than 2,000 votes.

The result is still too close to call in the state, with a recount and legal challenges possible and more ballots yet to be counted, including those from military personnel stationed overseas.

The unprecedented dual runoff in Georgia could attract more than US$1 billion (S$1.35 billion) in political spending and bring in small armies of campaign volunteers, strategists and lawyers.

"You are talking about money in an unprecedented fashion," said Mr Rick Dent, a longtime political consultant who served as an aid to the late Zell Miller when he was Georgia's governor.

All four candidates are preparing for the next phase.

Ms Loeffler asked for campaign donations on Twitter and said, "Control of the Senate could come down to our race."

Dr Andra Gillespie, a political science professor at Emory University in Atlanta, said Republicans have had the advantage in past runoffs. But the demographic changes in Georgia, which also are reflected in the close presidential race, mean some of the previous metrics may not apply.

"This is a different day," she said.

Still, the odds favour the incumbent Republican Mr Perdue in a head-to-head race against Mr Ossoff, who lost a 2017 special election for an Atlanta-area House seat.

Ms Loeffler, who was appointed by Georgia's governor to fill the Senate vacancy left by Republican Johnny Isakson's retirement, secured a spot in the runoff over another Republican, Representative Doug Collins.

In doing so, she cast herself as a staunch conservative, boasting in an ad that she is to the right of Attila the Hun. Now, she also will have to appeal to moderate voters to prevail in her one-on-one runoff against Warnock, a preacher from Ebenezer Baptist Church, where Martin Luther King Jr was once the pastor.

The get-out-the-vote operation will be intense, since new voters can be registered up until 30 days before the runoff.

The dual runoffs will be unlike any elections the state has seen before, said Professor Kerwin Swint from Kennesaw State University.

"These races are both going to be national campaigns now, with the stakes incredibly high," Prof Swint said.

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