The 2012 United States House of Representatives elections in Missouri were held on Tuesday, November 6, 2012, and elected the eight U.S. representatives from the state of Missouri, a loss of one seat following the 2010 United States census. The elections coincided with the elections of other federal and state offices, including a federal quadrennial presidential election, concurrent statewide gubernatorial election, quadrennial statewide lieutenant gubernatorial election, and an election to the U.S. Senate.
A new congressional map was passed by the Missouri General Assembly on April 27, 2011. The map was vetoed by Democratic Governor Jay Nixon on April 30, but Nixon's veto was overridden by the General Assembly on May 4, making the plan law. The map effectively eradicated the former 3rd district, which had been represented by Democrat Russ Carnahan since 2005, splitting it between the districts represented by Republicans Blaine Luetkemeyer and Todd Akin and Democrat William Lacy Clay, Jr. The bulk of the old 9th district became the new 3rd district.
Democrat William Lacy Clay, Jr., who had represented Missouri's 1st congressional district since 2001, ran for re-election.
Fellow U.S. Representative Russ Carnahan, part of whose district was drawn into the 1st district, challenged Clay in the Democratic primary.
Republican Todd Akin, who had represented Missouri's 2nd congressional district since 2001, chose to run for the U.S. Senate rather than seek re-election.
3rd District Congressman Russ Carnahan briefly mulled over a run in this district, though the district was more Republican than his previous district, and he did not live in the district. A poll commissioned by Carnahan showed him being competitive with Ann Wagner and Ed Martin. The Democratic Congressional Campaign Committee had preferred that Carnahan run in the district, and considered him a member of the Frontline program for vulnerable members. Ultimately, he ran unsuccessfully for the 1st district.
Whitfield requested a recount, as the race was separated by less than 1%. By September 13, 2012, the recount was completed and Koenen was declared the winner.
Republican Blaine Luetkemeyer ran in the reconfigured 3rd district, which includes most of the 9th district he had represented since 2009.
Republican Vicky Hartzler, who represented the 4th district since January 2011, sought re-election. In redistricting, all of Boone, Cooper, Howard, and Randolph counties, and parts of Audrain County, were added to the 4th district, while Cole, Lafayette, Ray, and Saline counties were removed from the district.
Missouri's 5th Congressional district was perhaps the one most complicated by redistricting, and the legal challenges that have ensued. Democratic incumbent Emanuel Cleaver successfully won re-election.
Republican Jerry Nolte, who at first announced his intention to run in the 6th district, decided to run in the 5th. His residence lay on the court-contested border of the two districts.
Due to realignment following the 2010 U.S. census, the district spanned most of the northern portion of the state, from St. Joseph to Kirksville, and also included most of the state's portion of the Kansas City Metropolitan Area north of the Missouri River. Incumbent Sam Graves, who had represented the district since 2001, ran for reelection.
Incumbent Republican Billy Long, who had represented the district since 2011, ran for re-election.
Republican Jo Ann Emerson, who had represented Missouri's 8th congressional district since 1996, was challenged by Democratic nominee Jack Rushin and Libertarian nominee Rick Vandeven.