Could Trump’s last-minute endorsement prevail in Georgia’s high-stakes Senate race?

Just before 1 a.m. on Sunday after more than 450,000 Georgia voters had already cast their ballots during early voting, President Donald Trump dropped an endorsement in the state's marquee Senate race to unseat Democratic incumbent Sen. Jon Ossoff.

"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 had not weighed in on Tuesday's Republican primary runoff battle between Rep. Mike Collins and former football coach Derek Dooley -- a battle that will decide who will go up against Ossoff in what will be one of the nation's most closely watched races in November with control of the Senate in the balance.

Trump's 11th-hour endorsement puts him at odds with popular Republican Gov. Brian Kemp, 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.

But this is not the first time Trump and Kemp have found themselves going head-to-head. The yearslong feud between the two most important Republicans in Georgia politics began after Kemp refused to overturn the 2020 election results in Georgia, eventually resulting in Trump's failed effort to oust Kemp from the governor's mansion by endorsing a primary challenger in 2022.

The 2020 presidential election remains at the center of Tuesday's race nearly six years later: In his late-night 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 consenual.

"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.

It is also a test of Kemp's own political power, as the Georgia governor has not ruled out a 2028 presidential run.

Just hours after Trump endorsed Collins, Kemp put even more of his political influence on the line by making an endorsement in Tuesday's GOP primary runoff for governor after staying neutral in the race between Lt. Gov. Burt Jones and billionaire businessman Rick Jackson that has been defined by an onslaught of razor-sharp attack ads dominating Georgia's airwaves.

"This fall, Georgians will have a clear choice to make in their next governor. I believe Burt Jones will make a strong case to the voters for four more years of conservative leadership that ensures our state's best days are ahead," Kemp wrote in a statement on X, putting him on the same side as the president in what has become the most expensive GOP gubernatorial race in Georgia's history with over $150 million in spending, according to AdImpact.

Unlike in the Senate runoff, both Republican candidates for governor have courted favor with Trump's base throughout the race. But only Jones, a longtime Trump loyalist who tried to help overturn the 2020 election, boasts Trump's endorsement.

In a cycle where Trump-endorsed candidates have prevailed against Republican incumbents like Sen. Bill Cassidy of Louisiana and Rep. Thomas Massie of Kentucky, Gillespie says that the moderate wing of Georgia's GOP might hold more power in Georgia compared to other states -- as evidenced by Kemp's ability to survive Trump's ire and get re-elected to a second term in 2022.

"In the South in particular, with the exception of Texas and Florida, Georgia's actually incredibly diverse, which makes Democrats more competitive in the state, even if they're still numerically the smaller group. And what that has done is that has lent itself to Republicans being pragmatists," Gillespie said.

But at the end of the day, Trump still has a lot of support among Republicans in Georgia, and Gillespie says Trump's last-minute endorsement could carry a lot of weight.

"I think it could be a question of whether or not that's too little, too late," Gillespie said.