Republican Clay Fuller is projected to have won Georgia's runoff election to replace former Congresswoman Marjorie Taylor Greene, a once-staunch ally of Donald Trump who resigned earlier this year after breaking with the president.

Fuller won the election to replace her on Tuesday, according to CBS News, the BBC's US partner. He is a Trump-endorsed candidate who won against Democrat Shawn Harris, and whose victory keeps the staunchly conservative district in Republican hands.

The win shores up the party's razor-thin 217-214 majority in the House of Representatives.

Fuller, a lieutenant colonel in the Georgia Air National Guard, will serve out the rest of Greene's term, which ends next January.

A special election was held on 10 March where Harris performed marginally better than Fuller, in part because a crowded Republican field split the vote. No single candidate won a majority that night, requiring Tuesday's run off election.