FIRST ON FOX: Firebrand Rep. Madison Cawthorn is endorsing Ohio Senate candidate Josh Mandel Monday as yet another national figure gets involved in the Buckeye State's high-profile GOP primary.

"Josh Mandel is a true Conservative who has proudly fought for America overseas and in public office," Cawthorn, R-N.C., said in a statement. "It is vitally important that true, America First, Conservatives take a majority in 2022 and I would ask that you join me in supporting Josh to do just that."

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Republican Senate candidate and former Ohio treasurer Josh Mandel speaks to the Geagua County Conservative Club in Chesterland, Ohio, on May 20, 2021. (Josh Mandel Senate campaign)

"I am honored to have Madison’s support for my U.S. Senate campaign," Mandel said. "Madison is a leader in the America First movement and I look forward to going to Washington to serve as reinforcements for him and other Conservative Pro-Trump warriors in the House and Senate."

Mandel is the former treasurer of Ohio and one of several GOP candidates in the combustible primary to replace retiring Sen. Rob Portman.

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Cawthorn's endorsement notably splits from that of another high-profile Trump-aligned House member, Rep. Marjorie Taylor Greene, R-Ga. She backed Hillbilly Elgy author J.D. Vance. Other GOP candidates including former Ohio GOP chairwoman Jane Timken, state Sen. Matt Dolan and venture capitalist Mike Gibbons are also considered viable candidates and getting backing from other state and national Republican figures.

Representative Madison Cawthorn, a Republican from North Carolina, speaks during the Conservative Political Action Conference (CPAC) in Dallas, Texas, U.S., on Friday, July 9, 2021. (Dylan Hollingsworth/Bloomberg via Getty Images)

Rep. Madison Cawthorn, R-N.C., is seen in the Capitol Visitor Center before Rep. Elise Stefanik, R-N.Y., won the election for House Republican Conference chair on Friday, May 14, 2021. (Tom Williams/CQ-Roll Call, Inc via Getty Images)

"In order to take back the Senate this fall, we must send fighters with backbone and courage who are unafraid of the radical Left and focused on advancing President Trump’s America First agenda," Mandel added of Cawthorn's endorsement. "That’s exactly what I will do in the U.S. Senate."

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Mandel is also backed by sitting Sens. Cynthia Lummis, R-Wyo., and Mike Lee, R-Utah, ex-Trump national security adviser Michael Flynn, and several other conservative groups and media figures.

"I’m confident I’m going to be the next United States senator from Ohio. I am the only candidate who’s been unwavering in my support for President Trump and the Trump America First agenda," Josh Mandel told Fox News during an interview at CPAC.

Ohio GOP Senate showdown: Firebrand Rep. Cawthorn endorses Josh Mandel in crowded Republican primary

Cawthorn said Senate needs 'true, America First, Conservatives'