Long's advisers include Jamestown Associates, the prominent Republican media firm that crafted ads for Trump’s presidential campaigns, and Caroline Wren, who was a top fundraiser on Trump’s reelection effort. Long has also signed on Kellyanne Conway, who was counselor in the Trump White House and managed the final months of his 2016 campaign, to serve as a senior adviser.

Conway, who is also advising several other 2022 candidates, is listed on an invitation as the special guest at a donor event Long is holding next week in Springfield, Mo.

The 65-year-old Long, who is running to replace retiring GOP Sen. Roy Blunt, joins a Republican primary field that includes state Attorney General Eric Schmitt, attorney Mark McCloskey, Rep. Vicky Hartzler, and former Gov. Eric Greitens. Earlier Tuesday, Rep. Ann Wagner announced that she would not be joining the primary, instead running for reelection in her district. But with so many candidates already in the race, the competition for donors is on: Long is sending out invitations to next week’s fundraiser showcasing a host committee of nearly 100 major givers, including Bass Pro Shops executive Johnny Morris and trucking company owner Robert Low.

Trump has yet to endorse a candidate in the race, though he has been in regular contact with Missouri Sen. Josh Hawley about how to engage in the contest. Hawley, who has received outreach from all the major Republican candidates, has so far given no indication of who he may support.

In a state that Trump won by 15 points, the candidates are going to great lengths to prove their allegiance to the former president. Just this week, a super PAC aligned with Schmitt began running a digital advertisement with an image of him standing alongside Trump. Greitens, meanwhile, recently campaigned with Trump’s former personal attorney, Rudy Giuliani, and Kimberly Guilfoyle, Donald Trump Jr.'s girlfriend, signed on as Greitens' national campaign chair. In June — weeks prior to his Senate campaign announcement — Long traveled with Trump to the southern border.

There is widespread concern within top GOP circles about Greitens, who left office in 2018 following allegations that he sexually assaulted a woman. A Greitens primary win, many party officials worry, could give Democrats an opening to win the general election in a state where they would likely struggle to compete otherwise. That, in turn, would jeopardize the GOP’s prospects of seizing the majority in the Senate, which is currently split 50-50.

Long appeared to take an implicit swipe at Greitens in his Wednesday evening announcement.

“We need to get the Senate back, you’re not going to get anything until you get the Senate back, and I’m the guy that can win that Senate seat in Missouri and make sure that we don’t have a big race there,” Long told Fox's Carlson.

Greitens has struggled to raise money, though he has the backing of Richard Uihlein, a billionaire shipping and industrial supply company executive who is one of the Republican Party’s biggest givers. Other major donors who’ve engaged in the race include tech investor Peter Thiel, who contributed to the Schmitt-aligned super PAC.