President-elect Joe Biden is urging Georgia voters to send two Democrats to Washington in Tuesday run-offs that will decide control of the US Senate.
President Donald Trump, meanwhile, has prepared his own pitch to keep the chamber in Republican hands.
The Georgia races respectively pit incumbent Republicans, Kelly Loeffler and David Perdue, against Democratic challengers Raphael Warnock and Jon Ossoff.
“It’s a new year and tomorrow can be a new day for Atlanta, for Georgia and for America,” Biden said at his event in the state’s capital, while criticising the outgoing president.
He said the Trump administration had “gotten off to a god-awful start” with the slow rollout of COVID-19 vaccines.
The president spends more time whining and complaining than doing something about the problem.”
He said the Democratic candidates, if elected, would ensure $US2000 ($A2600) stimulus cheques were delivered to Americans as the economy struggles.
Long solidly Republican, Georgia surprised the nation in November by backing a Democratic presidential candidate for the first time in almost three decades.
That has raised liberals’ hopes for Warnock and Ossoff, although they face an uphill battle and need twin victories to deny Republicans a Senate majority they could use to block Biden’s legislative agenda.
Later on Monday, Trump was due to address a rally in Dalton, a city in Georgia’s heavily Republican northwest.
The duelling appearances illustrate the high stakes of the contest, in which 3 million have already voted.
A sweep by the two Democrats would hand control to Biden’s party, as Vice President-elect Kamala Harris would hold the tiebreaking vote in the 50-50 chamber.
That would make it easier for Biden to enact further coronavirus relief and tackle climate change, as Democrats also control the House of Representatives.
None of the Senate candidates won a majority in the November 3 election, which spurred the run-off elections.
Trump continues to assert, without evidence, that his loss in November was the result of widespread voter fraud – a claim soundly rejected.
In a call on Saturday to Georgia Secretary of State Brad Raffensperger, Trump pressured the Republican official to “find” enough votes to overturn his defeat.
He suggested Raffensperger’s failure to alter the November results could hurt Republican turnout in the Senate runoffs.
Democrats and election experts say Trump’s efforts almost certainly broke the law.
Biden, who won Georgia by almost 12,000 votes, did not mention the call directly on Monday.
Loeffler said on Monday night she would object to the certification of the election results in Congress on Wednesday, joining about a dozen other Republican senators and over 100 Republican House members.
The move has virtually no chance of overturning Biden’s victory.
It is not clear whether Trump’s actions and his repeated claims of election fraud will affect the outcome of the Senate races.
Strategists say the outcome could likely hinge on how many Republican voters participate on Tuesday, given strong Democratic early turnout.
Results not expected for days after polls close
The outcome of the run-off races might not be known for days after polls close on Tuesday.
Public opinion polls show Republican incumbents Loeffler and Perdue have about the same level of support as Democratic challengers Warnock and Ossoff.
Slow counting of Georgia’s mail ballots in November’s presidential election kept the world in the dark about who won the state until three days after polls closed. Biden ended up winning by less than 12000 votes out of about five million cast.
A similar delay could unfold after Tuesday’s contests if the races are really close, says Walter Jones, a spokesman for the office of Georgia’s top election official, Secretary of State Brad Raffensperger.
“We may be looking at several days,” Jones said on Monday, adding that the delay would mostly come from mail ballots returned on election day.
Officials can’t start counting ballots until 7pm on Tuesday, though they have started processing them, such as checking that voter signatures on mail ballots match those on record.
Nearly a million mail-in ballots have been processed through Sunday, data shows.
These ballots, as well as more than two million cast in person at early voting centres, will likely be counted quickly on election night.
But for the mail votes that arrive on election day, officials will still need to open envelopes, check signatures and load the ballots in counting machines.
They will also need to process hundreds of thousands of votes expected to be cast in person that day.
In November, mail ballots heavily favoured Biden in Georgia and other swing states, while President Donald Trump led in votes cast in person.
If more Democrats again vote by mail this time, initial results could similarly show Republicans in a lead that gives way.
The slow counting of mail ballots was a key reason why Trump took an early lead on November 3, only to trail Biden in the days that followed.
In the end, about a quarter of Georgia’s ballots in November were cast by mail and Biden won about two-thirds. The rest were cast in person, with about 55 per cent going to Trump.
Georgia allows a losing candidate to force a recount if the margin of victory is less than or equal to 0.5 per cent.
A recount must be requested within two days of the results being certified by election officials.
Candidates can also request a recount if they think there has been an error in the tabulation; in that case it’s up to the secretary of state to decide whether to conduct one.