Deputy Secretary of State Jordan Fuchs confirmed the call between Trump and the elections investigator took place without offering details, saying only: "The secretary and the secretary of state's office can confirm that the call did happen."
The White House declined to comment to ABC News.
The individual familiar with the matter, who requested anonymity because of the sensitivity of the call, told ABC News that the president's call to the elections investigator occurred the day after White House Chief of Staff Mark Meadows traveled to Cobb County, Georgia, attempting to observe the signature match audit taking place there. The source asked that investigator remain unnamed because of the current threat environment election officials are facing.
Meadows was in the county on Dec. 22, ABC News previously reported. Fuchs said at the time that she did not allow Meadows to enter the room where investigators from Raffensperger's office and the Georgia Bureau of Investigation were doing the audit, but she did allow him to stand in the doorway.
Fuchs said that the president's chief of staff asked her "basic questions about the process," and also wanted to know if they were doing a statewide signature audit. Raffensperger had previously announced his office partnered with the University of Georgia to conduct a statewide signature audit study, which Fuchs said she told Meadows.
According to Fuchs, Meadows told her they had "a good meeting" and that whatever information she was able to provide to him, he would report back to Trump.
Raffensperger announced on Dec. 14 that Cobb County would conduct a signature audit, saying there were specific and credible allegations that signature matching wasn't done properly by election officials in the June primary.
A total of 15,118 absentee ballot oath envelopes, which is where voters sign, were randomly selected to be audited.
The audit was completed on Dec. 29, and investigators only found two ballots that should not have been accepted as they were. In Georgia, absentee by mail voters have the opportunity to cure a deficient absentee ballot, and the GBI said that these ballots should have gone through that process.
But the investigators also determined that neither of these ballots were fraudulently cast.
"I would also note for the record as well that during the course of the audit, there were no fraudulent absentee ballots identified in the process," GBI Director Vic Reynolds said in a press conference on Dec. 30.
In one instance, the voter's spouse signed the oath envelope on the voter's behalf; in the other, the voter signed the oath envelope in the wrong place.
In both cases, the audit team was able to contact both voters and confirm they had filled out their respective ballots themselves, Reynolds said.
Trump and allies, including the Georgia Republican Party chairman, repeatedly claimed that the signature rejection rate in Georgia for the general election was suspiciously lower than past elections, pointing to this as evidence of election fraud. But Raffensperger and other officials in his office have said this isn't true, and released figures to refute those claims.
Gabriel Sterling, the voting system implementation manager in Raffensperger's office, has previously said that those making incorrect assertions about signatures rejection rates are comparing "apples and oranges" because they are comparing the signature rejection rate to the full rejection rates from previous elections. The entire rejection rate includes absentee ballots that are received after the deadline, and Sterling said late arriving ballots account for the "vast majority" of rejected absentee ballots.
ABC News' Elizabeth Thomas contributed to this report.
Editor's note: Two months after this story was originally published, ABC News obtained a recording of then-President Donald Trump's call with Frances Watson, the chief investigator in Secretary of State Brad Raffensperger's office, via an open records request. ABC News had first reported that, according to an individual familiar with the matter, Trump phoned Watson during a signature match audit, telling her to "find the fraud" and that she would be a "national hero" for it. However, in the recording of the call, Trump does not say those exact words. This story and its headlines have been updated to remove those quotes.