2018 United States Senate elections

Among the 33 Class 1 Senate seats up for regular election in 2018, twenty-three were held by Democrats, two by independents who caucused with the Senate Democrats and eight by Republicans. Class Two seats in Minnesota and Mississippi held by interim appointees were also up for election; both incumbent appointees sought election to finish their unexpired terms.

Democrats targeted Republican-held Senate seats in Arizona (open seat) and Nevada.^[5] Seats in Texas,^[6] Mississippi (at least one of the two seats) and Tennessee (open seat)^[7] were also competitive for the Democrats. Republicans targeted Democratic-held seats in Indiana, Missouri, Montana, North Dakota and West Virginia, all of which were won by Republicans in both the 2012 and 2016 presidential elections.^[8] Seats in Florida, Ohio, Pennsylvania, Wisconsin and Michigan, all of which were won by Obama in 2008 and 2012 but by Trump in 2016, were also targeted by Republicans.^[5][9] The Democratic-held seat in New Jersey was also considered unexpectedly competitive due to corruption allegations surrounding the Democratic incumbent.

The map was widely characterized as extremely unfavorable to Democrats, as Democrats were defending 26 states while Republicans were defending nine. Of these seats, Democrats were defending ten in states won by Donald Trump in the 2016 presidential election, while Republicans were only defending one seat in a state won by Hillary Clinton in 2016.^[10][11][12] According to FiveThirtyEight, Democrats faced the most unfavorable Senate map in 2018 that any party has ever faced in any election.^[13][14]

Parties									Total
			Democratic	Republican	Independent	Libertarian	Green	Other
Last elections (2016)			46	52	2	0	0	0	100
Before these elections			47	51	2	0	0	0	100
Not up			23	42	0	—	—	—	65
	Class 2 (2014→2020)		11	20	0	—	—	—	31
	Class 3 (2016→2022)		12	22	0	—	—	—	34
Up			24	9	2	—	—	—	35
	Class 1 (2012→2018)		23	8	2	—	—	—	33
	Special: Class 2		1	1	0	—	—	—	2
	Regular elections
	Incumbent retired		0	3	0	—	—	—	3
		Held by same party	—	2	—	—	—	—	2
		Replaced by other party	1 Republican replaced by 1 Democrat						1
		Result	1	2	0	0	0	0	3
	Incumbent ran		23	5	2	—	—	—	30
		Won re-election	19	4	2	—	—	—	25
		Lost re-election	1 Republican replaced by 1 Democrat 4 Democrats replaced by 4 Republicans						5
		Result	20	8	2	0	0	0	30
	Special elections
	Appointee ran		1	1	—	—	—	—	2
		Appointee elected	1	1	—	—	—	—	2
		Result	1	1	0	0	0	0	2
	Total elected		22	11	2	0	0	0	35
	Net gain/loss		2	2					2
	Nationwide vote		52,224,867	34,722,926	808,370	590,051	200,599	1,262,765	90,473,222
		Share	58.17%	38.67%	0.90%	0.66%	0.22%	1.41%	100%
Result			45	53	2	0	0	0	100

Source: Clerk of the U.S. House of Representatives.^[1]

Each block represents one of the one hundred seats in the Senate. "D#" is a Democratic senator, "I#" is an independent senator and "R#" is a Republican senator. Arranged so parties are separated and a majority is clear by crossing the middle.

Each block indicates an incumbent senator's actions going into the election. Some "Ran" for re-election, some "Retired," and those without a note were not up for election this cycle. Before the elections, Republicans held 51 seats, Democrats held 47, and Independents held 2.

After the 2017 Senate special election in Alabama on the start of the second session in the 115th Congress.

Some senators were "Re-elected," some were a "Gain" in the seat from the other party (either by beating an incumbent or by winning an open seat), some were a "Hold" by the same party but with a different senator, and those without a note were not up for election this year.

After these elections, Democrats had 45 seats, independents had 2, and Republicans had 53.

Several sites and individuals publish predictions of competitive seats. These predictions look at factors such as the strength of the incumbent (if the incumbent is running for re-election) and the other candidates, and the state's partisan lean (reflected in part by the state's Cook Partisan Voting Index rating). The predictions assign ratings to each seat, indicating the predicted advantage that a party has in winning that seat.

Most election predictors used:

• "tossup": no advantage
• "tilt" (used by some predictors): advantage that is not quite as strong as "lean"
• "lean": slight advantage
• "likely" or "favored": significant, but surmountable, advantage
• "safe" or "solid": near-certain chance of victory

These are the election dates for the regularly scheduled general elections.

Three Republicans retired instead of seeking re-election.

Four Democrats and one Republican sought re-election but lost in the general election.

One Republican resigned before the start of the 116th Congress on December 31, 2018, and another Republican resigned during the 116th Congress for health reasons. Initially, all were replaced by Republican appointees.

In these special elections, the winners will be seated before January 3, 2019, when elected and qualified. They are ordered by election date, then by state and by class.

In these general elections, the winners were elected for the term beginning January 3, 2019.

All of the elections involve the Class 1 seats and they are ordered by state.

In twelve races the margin of victory was under 10% (although in California, the Senate race was fought between two members of the Democratic Party, Dianne Feinstein and Kevin de Leon, because of California's run-off system).

Arizona election

← 2012 2024 →
Turnout	64.85%
Nominee Kyrsten Sinema Martha McSally Party Democratic Republican Popular vote 1,191,100 1,135,200 Percentage 49.96% 47.61%
Sinema:      50–60%      60–70% McSally:      50–60%      60–70%      70–80%
U.S. senator before election Jeff Flake Republican Elected U.S. senator Kyrsten Sinema Democratic

One-term Republican Jeff Flake was elected with 49% of the vote in 2012. He chose not to run for re-election.^[30]

U.S. Representative Martha McSally^[31] won the Republican nomination in a three-way primary on August 28, 2018, against Joe Arpaio and Kelli Ward.

U.S. Representative Kyrsten Sinema^[31] easily secured the Democratic nomination.

Sinema defeated McSally by a slim margin; her victory became official only after six days of counting ballots.

California election

← 2012 2024 →
Turnout	56.42%
Nominee Dianne Feinstein Kevin de León Party Democratic Democratic Popular vote 6,019,422 5,093,942 Percentage 54.16% 45.84%
County results Feinstein:      50–60%      60–70% de León:      50–60%      60–70%      70–80%
U.S. senator before election Dianne Feinstein Democratic Elected U.S. senator Dianne Feinstein Democratic

Four-term Democrat Dianne Feinstein won a special election in 1992 and was elected to full terms in 1994, 2000, 2006, and 2012. She ran for re-election and advanced to the general election after securing the top spot in the June 5 jungle primary.^[33]

The June 5 primary ballot listed 32 candidates (Feinstein plus 31 challengers) in addition to 3 write-in candidates. There were 10 Democratic candidates, 11 Republican candidates, one Libertarian, one Peace and Freedom candidate, and 9 independent candidates. There was also a Green Party candidate who ran as a write-in.

President pro tempore of the California State Senate Kevin de León advanced to the general election for the right to challenge Feinstein after securing the second spot in the primary.^[33]

The 11 Republican candidates who ran in the primary combined for 33.2% of the vote. The top Republican candidate, James P. Bradley, received 8.3% of the vote, which put him in 3rd place at 3.8% behind the second-place finisher, Kevin DeLeon.^[34]

On November 6, Dianne Feinstein was elected to a fifth term, defeating Kevin de León.

Connecticut election

← 2012 2024 →
Turnout	63.58%
Nominee Chris Murphy Matthew Corey Party Democratic Republican Popular vote 825,579 545,717 Percentage 59.53% 39.35%
County results Municipality results Murphy:      40–50%      50–60%      60–70%      70–80%      80–90%      >90% Corey:      40–50%      50–60%      60–70%
U.S. senator before election Chris Murphy Democratic Elected U.S. senator Chris Murphy Democratic

One-term Democrat Chris Murphy was elected with 55% of the vote in 2012. He ran for re-election.^[35]

Businessmen Matthew Corey^[36] received the Republican nomination.

Chris Murphy was elected to a second term, winning nearly 60% of the vote.^[37]

Delaware election

← 2012 2024 →
Turnout	52.18%
Nominee Tom Carper Rob Arlett Party Democratic Republican Popular vote 217,385 137,127 Percentage 59.95% 37.81%
Carper:      50–60%      60–70% Arlett:      50–60%
U.S. senator before election Tom Carper Democratic Elected U.S. senator Tom Carper Democratic

Three-term Democrat Tom Carper won re-election with 66% of the vote in 2012. He announced he was running for re-election during an interview on MSNBC on July 24, 2017.^[38] He defeated Dover community activist Kerri Evelyn Harris for the Democratic nomination. Sussex County Councilman Robert Arlett won the Republican nomination.^[38]

Tom Carper defeated Arlett, winning 60% of the vote.^[39]

Florida election

← 2012 2024 →
Turnout	61.68%
Nominee Rick Scott Bill Nelson Party Republican Democratic Popular vote 4,099,505 4,089,472 Percentage 50.05% 49.93%
Scott:      50–60%      60–70%      70–80%      80–90% Nelson:      50–60%      60–70%
U.S. senator before election Bill Nelson Democratic Elected U.S. senator Rick Scott Republican

Three-term Democrat Bill Nelson was re-elected with 55% of the vote in 2012. He sought re-election to a fourth term in office.^[40]

Florida Governor Rick Scott won the Republican nomination. First elected in 2010 and re-elected in 2014, Scott's term as Governor of Florida was set to end by January 2019, due to term limits.^[40]

Edward Janowski was running as an independent, but did not qualify.^[40]

Scott led among ballots tallied on election night, but given the close margins of the race recounts were ordered.^[41] Final recount numbers were released following a machine and hand recount with Rick Scott maintaining a lead.^[42] On November 18, Nelson conceded to Scott.^[43] Two days later, election results were certified by the state, cementing Scott's win.^[44]

Hawaii election

← 2012 2024 →
Turnout	51.32%
Nominee Mazie Hirono Ron Curtis Party Democratic Republican Popular vote 276,316 112,035 Percentage 71.15% 28.85%
County results Hirono:      60–70%      70–80%
U.S. senator before election Mazie Hirono Democratic Elected U.S. senator Mazie Hirono Democratic

One-term Democrat Mazie Hirono was elected with 63% of the vote in 2012. She ran.^[45]

Ron Curtis was the Republican nominee.

Hirono was elected to a second term by a landslide.

Indiana election

← 2012 2024 →
Turnout	50.42%
Nominee Mike Braun Joe Donnelly Party Republican Democratic Popular vote 1,158,000 1,023,553 Percentage 50.73% 44.84%
County results Braun:      40–50%      50–60%      60–70%      70–80% Donnelly:      40–50%      50–60%      60–70%
U.S. senator before election Joe Donnelly Democratic Elected U.S. senator Mike Braun Republican

One-term Democrat Joe Donnelly was elected with 50.04% of the vote in 2012. He ran. He won the Democratic primary unopposed.^[46]

State Representative Mike Braun^[46] won the May 8 Republican primary. U.S. Representatives Luke Messer^[47] and Todd Rokita^[47] also ran for the Republican nomination.

James Johnson ran as an independent.^[46]

Braun won election with 51% of the vote, defeating Joe Donnelly.^[48]

Maine election

← 2012 2024 →
Turnout	59.96%
Nominee Angus King Eric Brakey Zak Ringelstein Party Independent Republican Democratic Popular vote 344,575 223,502 66,268 Percentage 54.31% 35.23% 10.45%
County results Municipality results King:      40–50%      50–60%      60–70%      70–80%      80–90%      >90% Brakey:      40–50%     50–60%      60–70%      70–80%      80–90%      >90% Tie:
U.S. senator before election Angus King Independent Elected U.S. senator Angus King Independent

One-term Independent Senator Angus King was elected in a three-way race with 53% of the vote in 2012. King has caucused with the Democratic Party since taking office in 2013, but he has left open the possibility of caucusing with the Republican Party in the future.^[49]

State Senator Eric Brakey ran unopposed for the Republican nomination.^[50]

Public school teacher and founder of UClass Zak Ringelstein ran unopposed for the Democratic nomination.^[50]

The election was conducted with ranked choice voting, as opposed to "First-past-the-post voting", after Maine voters passed a citizen referendum approving the change in 2016^[51] and a June 2018 referendum sustaining the change.^[52]

King was easily re-elected with over 50% of the vote.

Maryland election

← 2012 2024 →
Turnout	58.17%
Nominee Ben Cardin Tony Campbell Party Democratic Republican Popular vote 1,491,614 697,107 Percentage 64.86% 30.31%
Cardin:      40–50%      50–60%      60–70%      70–80%      80–90%      >90% Campbell:      50–60%      70–80%
U.S. senator before election Ben Cardin Democratic Elected U.S. senator Ben Cardin Democratic

Two-term Democrat Ben Cardin was re-elected with 56% of the vote in 2012. He won the Democratic primary.^[53]

Tony Campbell, Evan Cronhardt, Nnabu Eze, Gerald Smith, and Blaine Taylor^[54] were seeking the Republican nomination, with Campbell winning.

Arvin Vohra, vice chairman of the Libertarian National Committee, sought the Libertarian Party nomination.^[54]

Independents Neal Simon^[54] and Edward Shlikas^{[citation needed]}, and Michael B Puskar ran.

Cardin won re-election to a third term in office.^[55]

Massachusetts election

← 2012 2024 →
Turnout	59.17%
Nominee Elizabeth Warren Geoff Diehl Party Democratic Republican Popular vote 1,633,371 979,210 Percentage 60.34% 36.17%
County results Municipality results Warren:      40–50%      50–60%      60–70%      70–80%      80–90%      >90% Diehl:      40–50%      50–60%      60–70%
U.S. senator before election Elizabeth Warren Democratic Elected U.S. senator Elizabeth Warren Democratic

One-term Democrat Elizabeth Warren was elected with 54% of the vote in 2012. She ran for re-election.^[56]

State Representative Geoff Diehl,^[57] attorney and founder of Better for America, John Kingston^[57] and former Romney aide Beth Lindstrom,^[57] ran for the Republican nomination. Diehl won the Republican nomination.

Shiva Ayyadurai^[58] ran as an independent. Shiva started as in early 2017 as the first Republican in the race, but went independent in November 2017.

Warren defeated Diehl, winning a second term.^[59]

Michigan election

← 2012 2024 →
Turnout	56.72%
Nominee Debbie Stabenow John James Party Democratic Republican Popular vote 2,214,478 1,938,818 Percentage 52.26% 45.76%
Stabenow:      40-50%      50–60%      60–70%      70–80% James:      40–50%      50–60%      60–70%      70–80%
U.S. senator before election Debbie Stabenow Democratic Elected U.S. senator Debbie Stabenow Democratic

Three-term Democrat Debbie Stabenow was re-elected with 59% of the vote in 2012.^[60] She was renominated without Democratic opposition. On the Republican side, businessman John James won the nomination.^[60]

In the final months of the election, polls showed the race was beginning to narrow. Ultimately, Stabenow was re-elected, defeating James, with a majority of the vote.

Minnesota general election

← 2012 2024 →
Turnout	63.89%
Nominee Amy Klobuchar Jim Newberger Party Democratic (DFL) Republican Popular vote 1,566,174 940,437 Percentage 60.31% 36.21%
Klobuchar:      40–50%      50–60%      60–70%      70–80% Newberger:      40–50%      50–60%      60–70%
U.S. senator before election Amy Klobuchar Democratic (DFL) Elected U.S. senator Amy Klobuchar Democratic (DFL)

Two-term Democrat Amy Klobuchar was re-elected with 65% of the vote in 2012. She ran for re-election.^[61]

State Representative Jim Newberger^[61] ran for the Republican nomination.

Klobuchar was easily re-elected.^[62]

Minnesota special election

← 2014 2020 →
Turnout	63.66%
Nominee Tina Smith Karin Housley Party Democratic (DFL) Republican Popular vote 1,370,540 1,095,777 Percentage 52.97% 42.35%
Smith:      40–50%      50–60%      60–70% Housley:      40–50%      50–60%      60–70%
U.S. senator before election Tina Smith Democratic (DFL) Elected U.S. senator Tina Smith Democratic (DFL)

Two-term Democrat Al Franken announced that he would resign in December 2017, following allegations of sexual harassment. Mark Dayton, Governor of Minnesota, appointed Lt. Gov. Tina Smith on January 2, 2018, as an interim Senator until the November 2018 election. She defeated primary challenger Richard Painter in the Democratic primary held on August 14.

Incumbent Tina Smith defeated Republican Karin Housley in the general election to finish the term ending January 3, 2021.