In their endorsement, the Chamber praised Brunner's experience as the leader of the pharmaceutical firm Vi-Jon, where he served as CEO for 20 years.
"John Brunner is the best candidate in Missouri's U.S. Senate race who has what it takes to defeat Claire McCaskill, and the background to reverse her record of job loss, reckless government spending, and regulatory overreach," said U.S. Chamber Senior Vice President Rob Engstrom, adding that Brunner balanced budgets and created jobs at Vi-John.
Brunner is being challenged by Rep. Todd Akin and former state Treasurer Sarah Steelman for the party's nomination. The Brunner campaign hopes to use the endorsement to contrast with the political records of his two opponents.
"As Missouri's next citizen-Senator," Brunner said, "I will take my real-world experience in business and manufacturing to Capitol Hill and fight against big government so we can unleash entrepreneurs, innovators, and job creators to do what they do best and finally get America working again."
In addition to the Chamber's announcement, a handful of Missouri business owners also announced support for Brunner Tuesday. Dru Reeves, owner of a screen printing shop in Cape Girardeau, said he believes Brunner will "best represent" the interests of small businesses if elected.
"The most important issue in this election is getting our economy back on track and John Brunner is the man to help make that happen," Reeves said.
The Chamber is expected to play heavily in Missouri this year. McCaskill is one of the top targets of national Republicans who are hoping to take control of the U.S. Senate. Earlier in the year, the Chamber placed a significant television ad buy targeting McCaskill for her support of President Obama's hearth care law.
The Brunner campaign expects the Chamber to do a series public events across the state highlighting their endorsement in the coming weeks.