J.D. Vance arrives onstage at an election night event at Duke Energy Convention Center in Cincinnati, Ohio. AFP

Like many Republicans, the 37-year-old was initially critical of Trump during the latter's rise in politics -- at one point even calling him "America's Hitler" -- but later became an ardent supporter, emulating the former president's firebrand style of populism.

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A former Marine and graduate of the Ivy League Yale Law School, Vance first shot to fame with the publication of his 2016 memoir "Hillbilly Elegy," which sought to explain why working class white voters could be drawn to the candidacy of a New York real estate mogul like Trump.

Several candidates were vying for the Republican nomination in Ohio, with the race largely revolving around how close the party should remain to Trump, who still repeatedly claims he won the 2020 presidential election.

J.D. Vance arrives to speak to supporters next to his wife Usha Vance in Cincinnati, Ohio, US, on Tuesday. Reuters

Moderate Republicans, including outgoing Senator Rob Portman, fear that Democrats may be able to win the November general election if the Republican nominees support those unfounded claims.

"I've absolutely got to thank the 45th president of the United States, Donald J. Trump," Vance told his supporters in a victory speech.

"A lot of the fake news media out there ... wanted to write a story that this campaign would be the death of Donald Trump's America First Agenda. Ladies and gentlemen, it ain't the death of the America First Agenda!" said Vance.

In the November election, Vance will face off against moderate Democrat Tim Ryan, a sitting US representative from a blue-collar district.

Ohio's other sitting senator is Democrat Sherrod Brown, who has a similar style of politics to Ryan, giving hope to Democrats that they will be able to pick up a key Senate seat from the red-leaning state.

The US Senate is currently divided 50-50 between Republicans and Democrats, so each election this November holds the possibility of swinging control of the chamber.

Agence France-Presse