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2018 election analysis: Control of the U.S. Senate
Updated 9:15 a.m. EST, November 28, 2018
This content is part of Ballotpedia's analysis of the 2018 midterm elections. For comprehensive election results, click here.
2018 election analysis: Control of the U.S. Senate
Heading into the November 6, 2018, midterm election, Republicans held 51 of the 100 seats in the U.S. Senate, with Democrats holding 47, and two seats held by independents who caucus with Democrats. Democrats were defending 26 of the 35 seats up for re-election, making it difficult for them to add the two seats necessary to wrest majority control from the Republicans. This situation occurs occasionally. To read more about how a disproportion in the number of seats up for election impacted partisan risk in the 2016 elections, click here.
Republicans won Democratic seats in Florida, Indiana, Missouri, and North Dakota, while Democrats won Republican seats in Arizona and Nevada. Republicans will hold a 53-47 majority in the U.S. Senate in the 116th Congress.
Incumbents ran for re-election in 32 of 35 races. Five incumbent U.S. senators were defeated—four Democrats and one Republican. Democrats had to defend seats in 10 states that supported Donald Trump (R) over Hillary Clinton (D) in 2016, while Republicans had to defend just one seat in a state won by Clinton. All five of the incumbents who lost in 2018 were from those 11 states:
- North Dakota: U.S. Rep. Kevin Cramer (R) defeated incumbent Sen. Heidi Heitkamp (D). Trump won the state by 36 points in 2016.
- Missouri: Incumbent U.S. Sen. Claire McCaskill (D) lost to Missouri Attorney General Josh Hawley (R). Trump won Missouri by 18.5 percentage points in 2016. McCaskill's 2012 re-election was the last time a Democrat won a statewide election in Missouri.
- Indiana: Incumbent U.S. Sen. Joe Donnelly (D) lost to former state Rep. Mike Braun (R). Trump won Indiana by 19 points in 2016.
- Florida: Incumbent U.S. Sen. Bill Nelson (D) lost to term-limited Gov. Rick Scott (R). Trump won Florida by 1.2 percentage points in 2016.
- Nevada: Incumbent U.S. Sen Dean Heller (R) lost to U.S. Rep. Jacky Rosen (D). Clinton won Nevada by 2.4 percentage points in 2016.
See also
- 2018 election analysis: State government trifectas
- 2018 election analysis: Partisan balance of state legislative chambers
- 2018 election analysis: Incumbents defeated in state legislative elections
- 2018 election analysis: State legislative supermajorities
- 2018 election analysis: Partisan balance of governors
- 2018 election analysis: State government triplexes
- 2018 election analysis: Control of the U.S. House
- 2018 election analysis: Was 2018 a wave election?
Footnotes