The three-candidate race pitted two incumbents in a district redrawn by Missouri’s Republican-led legislature when the state lost a district after the 2010 Census. Candice Britton finished third.
Both men are members of prominent Missouri political families. William Lacy Clay Sr. represented St. Louis in the House for 32 years before his son took office after the 2000 election.
Carnahan’s grandfather served in Congress and his father was governor of Missouri before dying in a 2000 plane crash. Russ Carnahan first won election to the U.S. House of Representatives in 2004.
Six other members of Congress from Missouri were also on Tuesday’s primary ballot. Two ran unopposed, four were considered favorites.