The Oklahoma Republican runoff for Senate Tuesday is between two candidates who both pitch themselves as the America First candidate, and both accuse each other of being too political — though one has been in state government for much of his career, and the other has been in Congress for a decade.

Rep. Markwayne Mullin, R-Okla., secured former President Trump's endorsement just ahead of the Oklahoma primary in June, where he gained 43% of the vote, short of the 50% majority he needed to lock up the nomination in the deep-red state where the Republican nominee is expected to triumph in the November midterm elections. The runner-up in the primary, former state House speaker T.W. Shannon, sees his momentum growing as he crisscrosses the state, visiting towns where he says no politician has stopped before.

Though polls have shown Mullin with double a double-digit lead in the race, Shannon believes it will come down to turnout, and that voters will recognize what he sees as the heart of the race: Does Oklahoma want to vote someone into the Senate whose been in the Washington, D.C. "swamp" for a decade already?

"The problem with being in the swamp for 10 years — after you've been there for a long time, it doesn't stink to you," Shannon told Fox News Digital in an exclusive interview. "We've got a country to save, and in order to save people we've got to send people who are willing to fight not just for the sake of fighting, but who will stand up and be a disruptor, and will remind this country of what made it great to start with — capitalism, Christianity and the Constitution."

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Mullin, however, thinks it is Shannon who is the career politician. "What's at stake [in this election] is who do we want to represent us? Do we want the same old political background, the same resumé that that that we seem like we have a whole bunch of people like that in Washington, D.C.? I think all of us would agree we have enough attorneys in Washington, D.C.," Mullin told Fox News.

Mullin pitches himself as "a true citizen legislator" who is really going to fight for Oklahoma. He said his background in business and current work running a company with his wife means he has a greater connection with what people are actually struggling with every day. 

"When I get to the Senate, I'll still be the only current business operator in the Senate," Mullin said. "Now, there's a lot of successful people out there, but if you're not operating in this in today's atmosphere and today's atmosphere and the inflation that we're dealing with underneath the economic crisis we're dealing with, the labor shortages we're dealing with, and if you're not dealing with this overbearing regulatory environment that the Biden administration has put on us, and don't tell me you understand you might be a good listener, but you're not going to truly understand. You're going to have second hand knowledge."

To Shannon though, that is not enough and believes he is the better candidate to stand up not only to the Democratic Party leadership, but also the top Republicans in the Senate and House. He said he is the "only candidate in this race is going to push back against not just the liberals in Washington, but also the Republican establishment, because I believe that's as much a problem as anything else."

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"We have to have someone that's not just going to go to Washington, D.C. and go along to get along," Shannon said. "We need someone that's going to stand up to both Mitch McConnell, as well as Nancy Pelosi, as well as Chuck Schumer and as well as Kevin McCarthy. Listen, there's a natural contrast that exists between me and my opponent. My opponent has spent a decade in Washington, D.C. and, you know, and during that time, the debts continue to go up."

Mullin raised more than double what Shannon has in political fundraising ahead of the primary, according to Federal Election Commission filings. Mullin hauled in $2.3 million, while Shannon raised $1.1 million — though those figures do not represent fundraising during the runoff campaign period.

Oklahoma Sen. candidates T.W. Shannon and Rep. Markwayne Mullin

T.W. Shannon and Markwayne Mullin (Fox News)

Mullin, who was elected to the Oklahoma state House in 2006, went on to win a seat in Congress in 2012. He founded Mullin Plumbing in 1996 and still serves as president. Shannon was also first elected to the state House in 2006 and rose to be speaker in 2013. He lost a GOP runoff for U.S. Senate in 2014 to Sen. James Lankford and currently serves as CEO of Chickasaw Community Bank. 

With Trump's endorsement, Mullin says it is clear that he is the right candidate to fight for the America First message. 

"There's a reason why President Trump endorsed us because we know we're fighting for his agenda. But at the same time, one man can't do it by himself. It takes a whole bunch of like-minded individuals, which is why it's time we changed resume. Because if your background is politics, you're always going to make a political decision when push comes to shove," Mullin explained.

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Shannon says his record is unparalleled. He touted balancing state budgets, pushing welfare reform, fighting common core, pushing national voter ID laws and serving as the national chair of Black Voices for Trump. He said Trump made the wrong endorsement in his race — and others.

"But we also know the president doesn't always get it right when it comes to endorsements. He also endorsed Mitt Romney in 2016. In 2020. So the president's endorsement doesn't always produce the most America first candidate. And that's certainly the case in this race. That's how we make America great again is not through fighting just for the sake of fighting or through personal insults."