US President Donald Trump said Georgia Secretary of State Brad Raffensperger was "crazy" and not a Republican after a recording of a phone call between the two men was leaked.
Mr Trump spoke at a rally in Georgia amid revelations that he had pressured Mr Raffensperger, demanding that his fellow Republican "find" enough votes to overturn President-elect Joe Biden's victory in the Southern state
Mr Raffensperger and Georgia Governor Brian Kemp “say they're Republicans; I don’t think they are”, Mr Trump told a crowd in Dalton, a heavily Republican area in north Georgia.
“I'll be here in a year and a half campaigning against your governor and your crazy secretary of state.”
In the secretly taped conversation, which was first reported by The Washington Post, Mr Trump used threatening language against Mr Raffensperger and repeated claims that he won in Georgia.
Mr Trump and his Democrat successor Mr Biden led rallies in the Southern state on Monday before a run-off vote that will decide which party controls the 100-seat US Senate.
A double win for Democrats in Tuesday’s election would leave the Senate split 50-50, giving the tiebreaking vote and effective control of the chamber to Democrats, making it easier for the incoming Biden administration to pursue its legislative agenda.
At a campaign rally in Atlanta, Mr Biden said electing Democrats Rev Raphael Warnock and Jon Ossoff in the Georgia vote would enable his party to provide $2,000 Covid-19 stimulus checks to Americans.
“If you send Jon and the reverend to Washington, those $2,000 cheques will go out the door, restoring hope and decency and honour for so many people who are struggling right now,” said Mr Biden
Sending the incumbent Republican senators David Perdue and Kelly Loeffler “back to Washington” would mean “those cheques will never get there”, added Mr Biden, who takes control of the White House on January 20.
While Mr Perdue and Ms Loeffler have come out in support of the $2,000 cheques, a bill that would have increased direct stimulus payments from $600 to $2,000 was squashed by Senate Majority Leader Mitch McConnell, a Republican, last week.
Georgia voters are returning to polling centres on Tuesday for two run-off votes because none of the candidates received more than 50 per cent of the vote in the November 3 general election.
A record-breaking three million Georgia voters cast ballots during the early voting period, which ended Thursday. Tens of millions of dollars have poured into the state for a blitz of political television ads.
A double win for Democrats in Georgia would make it easier for Mr Biden to pass laws on health care, immigration, climate change and other issues. Polling in both races is tight, meaning the chances of a double-Democrat win are slim.
In the November 3 general election, the Georgia results were so close that it took 10 days for television networks to project Mr Biden had won the state. The results of the senate run-off votes could be similarly slow, analysts say.