FIRST ON FOX:  U.S. Senate candidate Markwayne Mullin of Oklahoma, a Republican who represents the state's 2nd Congressional District, recently met with former President Trump as Mullin campaigns in an increasingly crowded and competitive race.

Mullin, who has served in Congress since 2013, met with Trump at Trump's Mar-a-Lago estate April 14, just before a former Trump cabinet member entered the crowded Oklahoma special election to finish retiring Sen. Jim Inhofe's Senate term.

Trump has not publicly backed any of the candidates in the Oklahoma race, but his endorsements have been hotly sought after by Republican candidates hoping to get an edge over competitors for their party's nomination. Trump has used his support to show who is most aligned with his America First vision and who he believes is most likely to succeed in the general election against a Democratic opponent.

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Rep. Markwayne Mullin, R-Okla., met with former President Trump in April amid Mullin's campaign for Senate. (Markwayne Mullin for Senate )

At the meeting, Trump and Mullin discussed the state of the economy and the upcoming election, Mullin's campaign said. The Oklahoma congressman also showed Trump internal polling from his campaign that indicates he is far ahead of any other candidate in the race.

Mullin's meeting with Trump came one day before former Environmental Protection Agency administrator Scott Pruitt announced he would run for the Senate seat.  

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"I offer the experiences I had serving in the president's cabinet, serving as attorney general, making a difference on behalf of these issues that matter to Oklahomans today and, I think, matter to the people of this country," Pruitt said while registering his candidacy April 15. 

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Then-Environmental Protection Agency Administrator Scott Pruitt appears before a Senate Appropriations Subcommittee on the Interior, Environment and Related Agencies on budget on Capitol Hill in Washington.  (AP Photo/Andrew Harnik, File)

Pruitt said he recognized the experience of others in the race but said he "couldn't stand idly by and let what's happening in Washington, D.C., to continue," adding that "we need courage, we need conviction and we need civility" in the nation's leadership. 

Pruitt resigned from the EPA in 2018 following a series of controversies about his leadership of the agency.

Mullin also announced the members of his financial advisory team Saturday. They include a host of Oklahoma business owners who said the candidate would be a champion for small businesses. The finance committee includes oil entrepreneur and Trump donor Harold Hamm, according to a press release shared first with Fox News Digital.

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"Markwayne Mullin built a successful private-sector business before entering politics. He understands how to make a payroll and how to meet a budget. We need a businessman in the United States Senate," said Hastings Siegfried, an executive with aerospace giant NORDAM.

In the crowded field of candidates, Trump's support could push a contender to the top of the field in the June 28 primary. If no candidate receives over 50% of the vote, the top candidates will go to a runoff in August. 

Along with Pruitt, another Trump administration veteran is vying for the Oklahoma Senate seat. Alex Gray, former chief of staff for the National Security Council under Trump, has racked up a series of endorsements from Trump officials, including former ambassador to Germany Ric Grenell, former Department of Defense chief of staff Kash Patel and former national security adviser under Trump, Robert O'Brien, the Washington Examiner first reported.

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Rep. Markwayne Mullin (Greg Nash/Pool via REUTERS)

Inhofe, 87, announced in February he would retire at the end of 2022, leaving four years of his term unfinished and triggering a special election in Oklahoma. He immediately endorsed his former Senate aide, Luke Holland, in the race to fill his seat.

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Holland, 35, is a first-time candidate, and his professional experience has been dominated by his work on Inhofe's staff. After graduating from the University of Arkansas, Holland said, he started in Inhofe's Washington, D.C., mailroom in 2009, rising to become chief of staff in 2017.

"I'm just really excited to get in the race and to fight for the things that we hold so dear here in Oklahoma that are being ripped apart by the socialists and the left," Holland told Fox News Digital in an interview earlier this year.

Other candidates in the race include Michael Coibion, State Sen. Nathan Dahm, Jessica Jean Garrison, Randy J. Grellner, Adam Holley, Laura Moreno, Paul Royse, Oklahoma's first black state House Speaker T.W. Shannon and John F. Tompkins.

Fox News' Kelly Laco and Kyle Morris contributed to this story.