Congressman Kenny Hulshof defeated state Treasurer Sarah Steelman in the Missouri Republican gubernatorial primary.
With 98 percent of the precincts reporting results, Hulshof received about 49 percent of the vote, to Steelman's 45 percent.
Attorney General Jay Nixon won the Democratic nomination for governor with 85 percent of the vote.
In January, GOP Governor Matt Blunt announced he would not seek re-election.