Trump-endorsed Rep. Mike Collins wins Georgia GOP runoff to take on Democratic Sen. Jon Ossoff: AP projects

 Georgia Rep. Mike Collins, who was endorsed by President Donald Trump just days ago, is projected to win the runoff for the GOP nomination for the U.S. Senate and take on Democratic Sen. Jon Ossoff in the fall, according to the Associated Press.

With about 59% of the expected vote counted, Collins led Derek Dooley 55% to 45%, according to the AP.

Dooley, a former football coach, had been endorsed by Georgia Gov. Brian Kemp.

Collins is now projected to face off against Ossoff, the Democratic incumbent, in November, in what is expected to be one of the most competitive -- and most expensive -- races on the map in 2026. Democrats need to keep Ossoff's seat if they have any chance of taking the Senate, and Republicans see the Georgia seat as one of their best Senate pick-up opportunities.

"It is my Great Honor to endorse "MAGA" Mike Collins, a Highly Respected Congressman who has been with me from the very beginning," the president wrote on his social media platform.

Trump's endorsement put him at odds with Kemp, the popular outgoing governor, who endorsed Dooley -- a former University of Tennessee football coach and son of legendary University of Georgia football coach Vince Dooley -- early on in the race after deciding against running for the seat himself. Kemp is term-limited and will be leaving the governor's mansion at the end of this year after serving two terms.

This race was major a test of Kemp's political power as the Georgia governor has not ruled out a 2028 presidential run and spent the bulk of the campaign crisscrossing the state with Dooley and throwing the full force of his political operation behind the political novice. The 2020 presidential election remained at the center of Tuesday's race nearly six years later: In his endorsement of Collins, Trump called out Dooley -- who has branded himself as a political outsider -- for acknowledging that Joe Biden won the state at a campaign event in February.

"[Dooley] said that I lost Georgia in 2020 when, in actuality, the facts have now proven that I won by a lot!" Trump wrote.

Georgia officials audited and certified the results for a Joe Biden victory following the election and numerous lawsuits challenging the election results in the state were rejected by the courts.

Even before Trump's endorsement, the race between the "MAGA" firebrand Collins and the Kemp-backed outsider Dooley was widely seen as a proxy battle between the two wings of Georgia's Republican Party. Collins has touted his loyalty to Trump throughout his campaign, heavily courting Georgia's "Make America Great Again" base. The conservative congressman is known for his controversial social media presence, which has attracted scandal -- just last month, Collins fired one of his staffers after his official campaign account made a social media post mocking a Dooley campaign adviser whose wife attempted suicide after accusing former NBC anchor Matt Lauer of rape. Lauer has denied the allegations and said the encounter was consensual.

"The big issue or test for this runoff is whether or not the non-'MAGA' wing of the Georgia Republican Party retains some of its influence," Andra Gillespie, a political science professor at Emory University, told ABC News ahead of the run-off."[Dooley] said that I lost Georgia in 2020 when, in actuality, the facts have now proven that I won by a lot!" Trump wrote.

Georgia officials audited and certified the results for a Joe Biden victory following the election and numerous lawsuits challenging the election results in the state were rejected by the courts.

Even before Trump's endorsement, the race between the "MAGA" firebrand Collins and the Kemp-backed outsider Dooley was widely seen as a proxy battle between the two wings of Georgia's Republican Party. Collins has touted his loyalty to Trump throughout his campaign, heavily courting Georgia's "Make America Great Again" base. The conservative congressman is known for his controversial social media presence, which has attracted scandal -- just last month, Collins fired one of his staffers after his official campaign account made a social media post mocking a Dooley campaign adviser whose wife attempted suicide after accusing former NBC anchor Matt Lauer of rape. Lauer has denied the allegations and said the encounter was consensual.

"The big issue or test for this runoff is whether or not the non-'MAGA' wing of the Georgia Republican Party retains some of its influence," Andra Gillespie, a political science professor at Emory University, told ABC News ahead of the run-off.