Greene, a former MAGA diehard who's become a critic of President Donald Trump, announced in November that she'd be quitting Congress shortly into the new year. 

Last month, Republican Clayton Fuller and Democrat Shawn Harris were the top two vote-getters in the special election - in which candidates from both parties were listed on the ballot. 

Because neither candidate received above 50 percent, the race moved to a run-off stage. 

Since then, Republican-aligned groups have been funding ads to try and encourage GOP voters to show up to the polls. 

Punchbowl News reported Monday that outside Republican groups have spent more than $1.5 million on TV ads, digital ads and mailers to increase GOP turnout in a district that went for Trump by nearly 37 points. Greene won her district - against Harris - by nearly 29 points. 

If Harris can winnow that margin down to single digits it could suggest the GOP is in for a shellacking in the coming midterms, in which they're trying to hold onto their Congressional majority. 

Still, the Republican panic is likely overblown, with prediction markets giving Fuller a 98 percent chance of a win in the deep red district. 

Trump endorsed Fuller in a Truth Social post on February 4, but later appeared to forget that he had done so, while addressing reporters on Air Force One. 

'They say whoever I endorse is going to win. But we have a lot of good candidates that want to take her place,' Trump said on February 16. 

The White House wouldn't say whether Trump had forgotten that he had already made an endorsement in the race, instead pointing the Daily Mail to his original endorsement post.

Trump reposted the endorsement two days after the flight. 

The Daily Mail found that Fuller previously donated $250 to James Mackler, a former Democratic candidate for the US Senate. 

He also ran for Congress in 2020 and was endorsed by the With Honor Fund, a bipartisan group focused on electing military veterans with the aim of ending political polarization. 

The group has endorsed Democrats and anti-Trump Republicans, with Emma Bloomberg, the daughter of former New York City Mayor Michael Bloomberg, a Republican-turned-Democrat, sitting on the group's advisory board. 

Both Fuller and Harris are military veterans as the Iran war becomes a major voting issue.