Stacey Abrams' campaign on Sunday filed a federal lawsuit asking a judge to delay vote certifications in Georgia’s unsettled governor's race by one day and block counties from tossing some provisional and absentee ballots that may have minor mistakes on them.

Brian Kemp, her Republican challenger, issued a statement a day earlier calling for Abrams to concede. Kemp has declared victory and said it is "mathematically impossible" for her campaign to force a runoff.

Fox 5 Atlanta reported that Kemp is up by 59,000 votes. Kemp had 50.2 percent of the vote by early Monday.

Abrams, 44, has maintained that she will not concede until every vote has been counted, and pointed to the 5,000 votes tallied over the weekend that favored her. The Washington Post reported that she would need 21,700 additional votes to force a runoff.

The suit, if successful, would prevent officials from certifying county vote totals until Wednesday and could restore at least 1,095 votes that weren't counted. The campaign said thousands of more ballots could be affected.

"The bottom line is this race is not over. It is still too close to call, and we do not have confidence in the secretary of state’s office." — Lauren Groh-Wargo, Abrams’ campaign manager

Kemp's campaign did not have any immediate comment on the lawsuit, according to the station. The suit was filed over alleged problems in Democratic-favoring Gwinnett and DeKalb counties in metro Atlanta.

Dara Lindenbaum, a lawyer for Abrams’ campaign, said the suit intends to stop ballots with minor mistakes -- like the voter writing the day they filled out the ballot as their date of birth -- from being rejected.

But Kemp aides previously said Abrams has no path to victory and called her refusal to concede a "disgrace to democracy."

Each of Georgia's 159 counties must certify final returns by Tuesday, and many have done so already. Abrams hopes to delay the certification until Wednesday. The state must certify a statewide result by Nov. 20.

Lauren Groh-Wargo, Abrams’ campaign manager, told the Post, "The bottom line is this race is not over. It is still too close to call, and we do not have confidence in the secretary of state’s office."

Abrams hopes to become the nation's first black woman elected governor, while Kemp is trying to maintain GOP dominance in a diversifying state that could be important in the presidential election in two years.

"So her margin in those uncounted votes needs to be really high," Jeffrey Lazarus, who teaches political science at Georgia State University, said Sunday in an interview conducted by email. "To put it simply, she's running out of votes."

The Associated Press has not declared a winner.

Allegations by Abrams supporters of voter suppression, long voting lines and other balloting problems are hard to ignore given Kemp's "aggressively partisan conduct as secretary of state," said Michael Kang, who teaches election law at Northwestern University's law school.

"That said, I think the Abrams campaign still faces an uphill battle in first convincing a court about the need for a recount and second, having the recount net enough votes to force a runoff. As a general matter, recounts rarely end up changing the outcomes of elections," Kang, who previously taught at Emory University in Atlanta, said in an email interview to the Associated Press.

The Associated Press contributed to this report