Democratic candidate Raphael Warnock is projected to win the first of two nail-biting Senate races in Georgia, unseating Republican Kelly Loeffler.
With 98% of votes counted, US TV networks and the Associated Press news agency called the race for Mr Warnock.
Control of the Senate in the first two years of Democratic President-elect Joe Biden’s term will be determined by the outcome of the second runoff.
The result is a blow for outgoing Republican President Donald Trump.
The election is being rerun because none of the candidates in the November general election achieved the 50% needed for victory under state rules.
If confirmed, Mr Warnock would become the first black senator for the state of Georgia – a slavery state in the US Civil War – and only the 11th black senator in US history.
Claiming victory, Mr Warnock paid tribute to his mother, Verlene, who as a teenager worked as a farm labourer.
“The other day – because this is America – the 82-year-old hands that used to pick somebody else’s cotton went to the polls and picked her youngest son to be a United States senator,” he said.
Although Mr Biden’s Democrats would need to take both seats to gain full control of Congress, the Republican party of outgoing President Donald Trump needs only to win one in order to retain the Senate.
When will we get a result?
The candidates in both races have been in a dead heat heat, with 98% of ballots counted from Georgia’s 159 counties.
Mr Warnock has a wafer-thin lead over Ms Loeffler, while Republican David Perdue is tied with Democrat Jon Ossoff.
Thousands of votes remain to be counted in the Atlanta suburbs such as DeKalb County, which is expected to go heavily for the Democrats. Georgia election official Gabriel Sterling told CNN that final results were expected by lunchtime on Wednesday (about 17:00 GMT).
More than three million votes – about 40% of the state’s registered voters – were cast before Tuesday. Early voting was a key benefit for Mr Biden in November’s White House election.
Meanwhile, Mr Trump – whose unsubstantiated claims that he was the victim of electoral fraud left Republican strategists worried about turnout in Tuesday’s Senate runoffs – continued to cast aspersions on the integrity of the vote in Georgia.
On Saturday, Mr Trump pushed Georgia’s top election official Brad Raffensperger, a fellow Republican, to “find” enough votes to overturn Mr Biden’s presidential election win in the state.
Source:Fiilafmonline/BBC
