2018 United States Senate election in Missouri

The 2018 United States Senate election in Missouri took place on November 6, 2018, to elect a member of the United States Senate to represent the State of Missouri, concurrently with other elections to the United States Senate, elections to the United States House of Representatives, and various state and local elections, including Missouri's quadrennial State Auditor election.

This was one of ten Democratic-held Senate seats up for election in a state Donald Trump won in the 2016 presidential election. Incumbent Democratic Senator Claire McCaskill ran for re-election to a third term. McCaskill easily won her party's nomination, defeating several minor candidates in the primary, while Missouri Attorney General Josh Hawley comfortably won the Republican primary.

The candidate filing deadline was March 27, 2018, and the primary election was held on August 7, 2018. Pollsters predicted a tight race, however Hawley defeated McCaskill on election day by 5.8%, taking 51.4% of the vote to McCaskill's 45.6%, a somewhat larger margin than expected. This resulted in Republicans holding both Senate seats in Missouri for the first time since McCaskill took office in 2007. Hawley was also the youngest incumbent senator at that time and continued to be until the inauguration of Jon Ossoff in 2021.

Nominated

 * Claire McCaskill, incumbent U.S. Senator

Eliminated in primary

 * Angelica Earl, former insurance verification specialist
 * David Faust
 * Travis Gonzalez, perennial candidate
 * John Hogan, perennial candidate
 * Leonard Steinman, perennial candidate
 * Carla (Coffee) Wright

Results
[[File:2018 MO US Senate Democratic primary.svg|thumb|Results by county: {{legend|#5f8dd3|McCaskill}}

{{legend|#214478|80–90%}}

{{legend|#2c5aa0|70–80%}}

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Nominated

 * Josh Hawley, Missouri Attorney General

Eliminated in primary

 * Austin Petersen, businessman and Libertarian candidate for presidential nomination in 2016
 * Brian Hagg
 * Bradley Krembs
 * Tony Monetti, retired bomber pilot and assistant dean of aviation at University of Central Missouri
 * Kristi Nichols, activist and candidate for the U.S. Senate in 2010 and 2016
 * Ken Patterson, candidate for St. Louis County Executive in 2010
 * Peter Pfeifer
 * Fred Ryman, Constitution nominee for the U.S. Senate in 2016
 * Christina Smith
 * Courtland Sykes, veteran and former congressional aide

Withdrew

 * Camille Lombardi-Olive, Democratic candidate for MO-07 in 2016

Declined

 * Ann Wagner, U.S. Representative and former U.S. Ambassador to Luxembourg
 * Aaron Hedlund, economics professor
 * Paul Curtman, state representative
 * Eric Greitens, former Governor of Missouri
 * Vicky Hartzler, U.S. Representative
 * Todd Richardson, Speaker of the Missouri House of Representatives
 * Eric Schmitt, state treasurer
 * David Wasinger, attorney
 * Marsha Haefner, state representative
 * Ed Martin, former chairman of the Missouri Republican Party, nominee for MO-03 in 2010 and nominee for attorney general in 2012

Results
[[File:2018 MO US Senate Republican primary.svg|thumb|Results by county: {{legend|#d35f5f|Hawley}}

{{legend|#c83737|60–70%}}

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{{legend|#de8787|40–50%}} {{legend|#decd87|Monetti}}

{{legend|#decd87|40–50%}} ]]

Nominated

 * Japheth Campbell, entrepreneur

Withdrew

 * Don Donald
 * Dennis Lagares

Declined

 * Alicia Dearn, attorney and candidate for Vice President of the United States in 2016
 * Austin Petersen, Libertarian candidate for President of the United States in 2016 (running as a Republican)

Results
[[File:2018 MO US Senate Libertarian primary.svg|thumb|Results by county: Campbell

{{legend|#554400|100%}} No votes

{{legend|#000000|No votes}} ]]

Nominated

 * Jo Crain

Eliminated in primary

 * Jerome Bauer

Results
[[File:2018 MO US Senate Green primary.svg|thumb|Results by county: {{legend|#2aff80|Crain}}

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{{legend|#00aa44|80–90%}}

{{legend|#00d455|70–80%}}

{{legend|#00ff66|60–70%}}

{{legend|#2aff80|50–60%}} {{legend|#999999|Crain/Bauer tie}}

{{legend|#999999|50%}} {{legend|#ff2ad4|Bauer}}

{{legend|#ff2ad4|50–60%}}

{{legend|#ff00cc|60–70%}}

{{legend|#d400aa|70–80%}}

{{legend|#aa0088|80–90%}}

{{legend|#550044|100%}} No votes

{{legend|#000000|No votes}} ]]

Declared

 * Craig O'Dear, attorney

Debates

 * Complete video of debate, October 18, 2018

Polling

 * with Austin Petersen


 * with generic Republican


 * with Vicky Hartzler


 * with Blaine Luetkemeyer


 * with Todd Richardson


 * with Eric Schmitt


 * with Jason Smith

Results
Sen. McCaskill conceded a few hours after the polls closed on Election Day. Despite performing strongly in the St. Louis suburbs, she ran well behind her 2012 vote in Southeast Missouri, especially in the Lead Belt and the Missouri Bootheel. She also ran poorly in the northern part of the state. Despite McCaskill's loss, Missouri Democrats held the other statewide office that went up for election in this cycle, the office of Missouri State Auditor. Democratic incumbent state auditor Nicole Galloway, who had been appointed to the post in 2015 by then-Gov. Jay Nixon following a vacancy, won a full term in the 2018 State Auditor election.

Counties that flipped from Democratic to Republican

 * Audrain (Largest city: Mexico)
 * Bates (Largest city: Butler)
 * Chariton (Largest city: Salisbury)
 * Clark (Largest city: Kahoka)
 * Clinton (Largest city: Cameron)
 * Daviess (Largest city: Gallatin)
 * Dunklin (Largest city: Kennett)
 * Franklin (Largest city: Washington)
 * Gentry (Largest city: Albany)
 * Grundy (Largest city: Trenton)
 * Henry (Largest city: Clinton)
 * Hickory (Largest city: Hermitage)
 * Howard (Largest city: Fayette)
 * Iron (Largest city: Ironton)
 * Knox (Largest city: Edina)
 * Lafayette (Largest city: Odessa)
 * Lewis (Largest city: Canton)
 * Linn (Largest city: Brookfield)
 * Livingston (Largest city: Chillicothe)
 * Madison (Largest city: Fredericktown)
 * Nodaway (Largest city: Maryville)
 * Pike (Largest city: Bowling Green)
 * Reynolds (Largest city: Ellington)
 * Schuyler (Largest city: Lancaster)
 * Scotland (Largest city: Memphis)
 * Scott (Largest city: Sikeston)
 * Shannon (Largest city: Winona)
 * St. Francois (Largest city: Farmington)
 * Sullivan (Largest city: Milan)
 * Wayne (Largest city: Piedmont)
 * Worth (Largest city: Grant City)
 * Buchanan (Largest city: St. Joseph)
 * Clay (Largest city: Liberty)
 * Jefferson (Largest city: Arnold)
 * Mississippi (Largest city: Charleston)
 * New Madrid (Largest city: New Madrid)
 * Pemiscot (Largest city: Caruthersville)
 * Ray (Largest city: Richmond)
 * Saline (Largest city: Marshall)
 * Washington (Largest city: Potosi)
 * Sainte Genevieve (Largest city: Ste. Genevieve)
 * St. Charles (Largest city: O'Fallon)
 * Platte (Largest city: Kansas City)
 * Pettis (Largest city: Sedalia)
 * Pulaski (Largest city: Fort Leonard Wood)
 * Adair (Largest city: Kirksville)
 * Andrew (Largest city: Savannah)
 * Cass (Largest city: Harrisonville)
 * Greene (Largest city: Springfield)
 * Johnson (Largest city: Warrensburg)