Marjorie Taylor Greene, a businesswoman and political newcomer, beat neurosurgeon John Cowan in a primary runoff in the staunchly Republican 14th Congressional District, which stretches from the outskirts of metropolitan Atlanta to the rural north-west corner of the state.
“Congratulations to future Republican Star Marjorie Taylor Greene on a big Congressional primary win in Georgia against a very tough and smart opponent,” Trump said on Twitter. “Marjorie is strong on everything and never gives up – a real WINNER!”
Ms Greene responded: “You inspired me to run and fight to Save America and Stop Socialism!! No one will fight harder than me!!”
She has amassed tens of thousands of followers on social media, where she often posts videos of herself speaking directly to the camera.
The videos have helped propel her popularity with her base, but have also drawn condemnation after footage surfaced in which she complains of an “Islamic invasion” of government offices, claims black and Hispanic men are held back by “gangs and dealing drugs”, and pushes an anti-Semitic conspiracy theory that billionaire philanthropist George Soros, who is Jewish, collaborated with the Nazis.
Ms Greene also is part of a growing list of candidates who have expressed support for QAnon, a conspiracy theory centred on the baseless belief that Mr Trump is waging a secret campaign against enemies in the “deep state” and a child sex trafficking ring run by satanic paedophiles and cannibals.
She will face Democrat Kevin Van Ausdal in November. Republican representative Tom Graves, who did not seek re-election, last won the seat with more than 76% of the vote in 2018.
