Thirty-five U.S. Senate seats, including two in special elections, are up for election on November 6, 2018.

Heading into the election, the Republican Party holds a 51-seat majority in the chamber. Democrats hold 47 seats, and the remaining two seats are held by independents who caucus with the Democratic Party.

The Democratic Party faces greater partisan risk in 2018, as they are defending 26 seats while Republicans are only defending nine. Additionally, the Democratic Party must defend seats in 10 states that supported Donald Trump (R) over Hillary Clinton (D) in the 2016 presidential election. Republicans are defending just one Senate seat in a state won by Clinton—Nevada.

Three incumbent senators, all Republicans, are not seeking re-election in 2018: Sen. Bob Corker (Tenn.), Sen. Jeff Flake (Ariz.), and Sen. Orrin Hatch (Utah).

Those elected to the U.S. Senate in the 33 regular elections on November 6, 2018, will begin their six-year terms on January 3, 2019.

Ballotpedia compiled the following resources to help voters better understand the U.S. Senate elections:

This page focuses mainly on general elections. For more in-depth information on the Democratic and Republican primaries by state, see the following pages.

Democratic Party United States Senate Democratic Party primaries, 2018

Republican Party United States Senate Republican Party primaries, 2018


Partisan breakdown

Heading into the election, the Republican Party holds the majority in the U.S. Senate with 51 Senate seats. Democrats have 47 Senate seats. Two seats are held by independents who caucus with the Democratic Party. In the 2016 elections, the Republican Party lost two seats but maintained its Senate majority.

U.S. Senate Partisan Breakdown
Party As of November 2018 After the 2018 Election
Democratic Party 47 Pending
Republican Party 51 Pending
Independent 2 Pending
Vacancies 0 Pending
Total 100 100


There are 24 Democratic seats, nine Republican seats, and two seats held by independents up for election in 2018. The Democratic Party will need to pick up two seats in the Senate in 2018 to regain the majority they lost in 2014. This is unlikely as there are so few Republican seats up for election.[2]


Click here for more of Ballotpedia’s coverage of U.S. Senate battleground races in 2018.


The following map displays which Senate seats are up for election in 2018 and identifies those races that are considered battleground elections. Mouse over a state for more detailed information.




United States Senate Battleground Races
State Incumbent
Arizona Republican Party Jeff Flake
California Democratic Party Dianne Feinstein
Florida Democratic Party Bill Nelson
Indiana Democratic Party Joe Donnelly
Minnesota (special) Democratic Party Tina Smith
Mississippi (special) Republican Party Cindy Hyde-Smith
Missouri Democratic Party Claire McCaskill
Montana Democratic Party Jon Tester
Nevada Republican Party Dean Heller
New Jersey Democratic Party Bob Menendez
New Mexico Democratic Party Martin Heinrich
North Dakota Democratic Party Heidi Heitkamp
Ohio Democratic Party Sherrod Brown
Tennessee Republican Party Bob Corker
Texas Republican Party Ted Cruz
West Virginia Democratic Party Joe Manchin



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