And beyond mastering the art of campaigning, he'll face the increased scrutiny that comes with a high-profile campaign for a competitive seat.
Only hours after the Brunner announcement, Akin's campaign manager pushed back against the idea that the businessman could take the mantle of an outsider.
"Congressman Akin has always been the outsider in Washington. The Congressman has been fighting the establishment and has the votes to back it up," Karl Hansen said. "If Mr. Brunner is looking for an outsider in the race, he should cast his ballot for Rep. Akin."
Akin, a staunch conservative who has positioned himself as such in the race, has been working at events across the state to build connections with new voters. While he has strong connections in the St. Louis area, near his Congressional district, he is less well-known statewide.
Steelman has struggled to gain momentum in her campaign, experiencing staff turnover and racking up an unenviable burn rate during the first two quarters of the year. According to Federal Election Commission records, she raised $387,000 from January to June but spent $395,000.
But she might end up with a gender and geographic edge. Brunner and Akin will likely have their strongest base of support in St. Louis, while she could pull strong numbers elsewhere in the state, including in central and southwest regions of Missouri. And some strategists think Steelman, as a woman, could make a case that she would have an edge in taking on McCaskill. Her campaign aides stress that a three-way race is a huge boost to Steelman's candidacy.
Third-quarter fundraising reports from Steelman and Akin, to be released later this month, will help illuminate where their campaigns stand.
Brunner has brought on well-known consultants for polling and media. Randall Gutermuth and Linda DiVall of American Viewpoint are very familiar with the terrain of the Show Me State and are leading his polling operation. Paul Curcio of SRCP Media is heading Brunner's media operation.
All of this does little to change the re-election challenge for McCaskill.
Democratic strategist Mike Kelley, a former executive director of the state party, said Brunner's entry doesn't change the dynamics of the Senate race.
"I don't think this changes the outlook for Claire much," he said. Perhaps telegraphing Democratic attacks, he said Brunner and Akin represent the "extremists" wing of the GOP that is "out of touch with mainstream Missouri." And he slammed Steelman as a "perennial candidate."
Sen. Jeff Flake, R-Ariz., takes a selfie with Faye, a pot belly pig, after a news conference held by Citizens Against Government Waste at the Phoenix Park Hotel to release the 2015 Congressional Pig Book which identifies pork-barrel spending in Congress, May 13, 2015.