JEFFERSON CITY, Mo. -- The U.S. Chamber of Commerce is wading into Missouri's Republican Senate primary by endorsing St. Louis businessman John Brunner.

The chamber said it's backing Brunner because his private-sector experience in cutting spending and balancing a budget could provide the greatest contrast with Democratic U.S. Sen. Claire McCaskill.

Brunner stepped down as chairman of Vi-Jon Laboratories Inc. shortly before announcing his Senate candidacy last fall. He is competing in the August Republican primary against former state treasurer Sarah Steelman and Congressman Todd Akin.

Akin has regularly received the chamber's annual "spirit of enterprise" award during the past decade, as have many Republican incumbents in Congress.

The chamber already has been running TV ads against McCaskill and has vowed to remain involved through the November election.