On stage at a debate organized by PoliticMo and the University of Missouri-Republicans College Republicans, he issue may have been the largest matter of disagreement between the hopefuls.
John Brunner, a St. Louis businessman who had never before sought public office, is hoping to position himself as a political outsider against two political figures. Earlier in the week, his campaign charged that if the Republican Party "doesn't nominate John," McCaskill will win in November.
Saturday, Brunner defended the charge, asserting his belief that the party should nominate someone with prior business experience, not political experience.
"You have to have a great organization and a great team to pull. You have to have the financial resources," Brunner said. "You have to have a great message. A great message is not another politician."
U.S. Rep. Todd Akin said he believes there is not time for "on the job" training for a legislative outsider like Brunner. However, Akin said the party's chances in November look good, regardless of the nominee.
"Everybody always says, 'if you don't elect me, we can't beat the Democrats.' I'm not as pessimistic as John, I think any of the three of us could beat this gal," Akin said.
Brunner has also criticized former state Treasurer Sarah Steelman, who is running as an "anti-establishment" candidate, as being of the very establishment she rails against. Steelman audibly laughed when pressed on the charge.
"That's laughable that I'm the establishment candidate since I've fought all of the establishment all of my life," Steelman said.
Steelman criticized Brunner for his use of political consultants, asserting that he is as political as anyone else.
"If you look at his campaign, he really is running the typical, political campaign," she said.
Brunner questioned both of his opponents, who have served significant time in legislative office and campaigning for higher office, for "running from this concept of career politician."
"These are definitions that are hard for me to understand," Brunner said, after listing off the former offices and campaigns of Akin and Steelman. "We cannot afford to have career politicians to get the job done."
Saturday's debate was likely the most heated exchange yet between the three candidates as the trio pivots from the Lincoln Day campaigning phase of the primary to the heated months of late spring and summer.
The trio is set to meet again Monday for its ninth get together at a forum in St. Charles.