2018 United States Senate elections

The 2018 United States Senate elections were held on November 6, 2018. Among the 100 seats, the 33 of Class 1 were contested in regular elections while two others were contested in special elections due to Senate vacancies in Minnesota and Mississippi. The regular election winners were elected to six-year terms running from January 3, 2019, to January 3, 2025. Senate Democrats had 26 seats up for election (including the seats of two Independents who caucus with them), while Senate Republicans had nine seats up for election.

To maintain their working majority of 50 senators and their party's vice president's tie-breaking vote, Republicans could only afford a net loss of one seat in these elections. The Republicans had a 52–48 majority after the 2016 elections, but they lost a seat in Alabama after Jeff Sessions resigned to become U.S. attorney general and Doug Jones, a Democrat, won in the subsequent special election. Three Republican-held seats were open as a result of retirements in Tennessee, Utah, and Arizona. Although every Democratic incumbent ran for re-election, Democrats faced an extremely unfavorable map, defending 26 seats, of which 10 were in states won by Donald Trump in the 2016 presidential election, in five states by more than 10%. Republicans, meanwhile, only had to defend nine seats, of which only one was in a state won by Hillary Clinton in 2016.

The Republicans increased their majority by defeating Democratic incumbents in Florida, Indiana, Missouri, and North Dakota, and holding the open seats in Tennessee and Utah. Democrats captured two Republican-held seats, defeating an incumbent in Nevada and winning the open seat in Arizona. This marked the first time that Republicans gained Class 1 Senate seats since 1994. To date, this remains the last time that Democrats won a Senate election in Montana, Ohio, and West Virginia.

The results for this election cycle were the only significant net gains made by the Republicans in what was otherwise characterized as a "blue wave" election. The Republican gains in the Senate and the Democratic gains in the House marked the first midterm election cycle since 1970 in which the president's party made net gains in one chamber of Congress while suffering net losses in the other, which also occurred in 1914, 1962, and 2022. This was also the first midterm election cycle since 2002 in which any incumbents of the non-presidential party lost re-election. The number of defeated non-presidential party incumbents (four) was the most since 1934.

Partisan composition 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. Seats in Texas, Mississippi (at least one of the two seats) and Tennessee (open seat) 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. 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. 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. According to FiveThirtyEight, Democrats faced the most unfavorable Senate map in 2018 that any party has ever faced in any election.

Senate Majority Leader Mitch McConnell decided to cancel the traditional August recess, which drew controversy. The US Congress traditionally goes on recess in the month of August each year, which in election years allows incumbents to leave Washington D.C. and campaign for re-election in their home state. The Democratic Party had a significantly larger number of vulnerable incumbent Senators, who became unable to campaign in person during the affected time period while their non-incumbent opponents were unaffected. The House of Representatives did not cancel their 2018 August recess.

Results summary

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 11 20 0 — — — 31 12 22 0 — — — 34 Up 24 9 2 — — — 35 23 8 2 — — — 33 1 1 0 — — — 2 Regular elections Incumbent retired 0 3 0 — — — 3 — 2 — — — — 2 1 Republican replaced by 1 Democrat 1 1 2 0 0 0 0 3 Incumbent ran 23 5 2 — — — 30 19 4 2 — — — 25 1 Republican replaced by 1 Democrat 4 Democrats replaced by 4 Republicans 5 20 8 2 0 0 0 30 Special elections Appointee ran 1 1 — — — — 2 1 1 — — — — 2 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.

Change in composition 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.

Before the elections 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.

D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D I I RMajority → R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R

After the elections 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.

D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D D I I R R RMajority → R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R R

Key: D Democratic R Republican I Independent, caucusing with Democrats

Predictions 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

Constituency Incumbent 2018 election ratings State PVI Senator Lastelection Cook IE Sabato NYT Fox News CNN RCP Daily Kos Politico 538 Result Arizona R+5 Jeff Flake | data-sort-value="49.2" | 49.2% R

| Sinema50.0% D California D+12 Dianne Feinstein | data-sort-value="-62.5" | 62.5% D

| Feinstein54.2% D Connecticut D+6 Chris Murphy | data-sort-value="-54.8" | 54.8% D

| Murphy59.5% D Delaware D+6 Tom Carper | data-sort-value="-66.4" | 66.4% D

| Carper60.0% D Florida R+2 Bill Nelson | data-sort-value="-55.2" | 55.2% D

| Scott50.1% R Hawaii D+18 Mazie Hirono | data-sort-value="-62.6" | 62.6% D

| Hirono71.2% D Indiana R+9 Joe Donnelly | data-sort-value="-50.0" | 50.0% D

| Cardin64.9% D Massachusetts D+12 Elizabeth Warren | data-sort-value="-53.7" | 53.7% D

| Warren60.3% D Michigan D+1 Debbie Stabenow | data-sort-value="-58.8" | 58.8% D

| Stabenow52.3% D Minnesota D+1 Amy Klobuchar | data-sort-value="-65.2" | 65.2% D

| Klobuchar60.3% D Minnesota D+1 Tina Smith | data-sort-value="0" | Appointed

| Smith53.0% D Mississippi R+9 Roger Wicker | data-sort-value="57.1" | 57.1% R

| Wicker58.5% R Mississippi R+9 Cindy Hyde-Smith | data-sort-value="0" | Appointed

| Hyde-Smith53.6% R Missouri R+9 Claire McCaskill | data-sort-value="-54.8" | 54.8% D

| Hawley51.4% R Montana R+11 Jon Tester | data-sort-value="-48.6" | 48.6% D

| Tester50.3% D Nebraska R+14 Deb Fischer | data-sort-value="57.8" | 57.8% R

| Fischer57.7% R Nevada D+1 Dean Heller | data-sort-value="45.9" | 45.9% R

| Rosen50.4% D New Jersey D+7 Bob Menendez | data-sort-value="-58.9" | 58.9% D

| Menendez54.0% D New Mexico D+3 Martin Heinrich | data-sort-value="-51.0" | 51.0% D

| Heinrich54.1% D New York D+11 Kirsten Gillibrand | data-sort-value="-72.2" | 72.2% D

| Gillibrand67.0% D North Dakota R+16 Heidi Heitkamp | data-sort-value="-50.2" | 50.2% D

| Cramer55.4% R Ohio R+3 Sherrod Brown | data-sort-value="-50.7" | 50.7% D

| Brown53.4% D Pennsylvania EVEN Bob Casey Jr. | data-sort-value="-53.7" | 53.7% D

| Casey55.7% D Rhode Island D+10 Sheldon Whitehouse | data-sort-value="-64.8" | 64.8% D

| Whitehouse61.5% D Tennessee R+14 Bob Corker | data-sort-value="64.9" | 64.9% R

| Blackburn54.7% R Texas R+8 Ted Cruz | data-sort-value="56.5" | 56.5% R

| Cruz50.9% R Utah R+20 Orrin Hatch | data-sort-value="65.3" | 65.3% R

| Kaine57.0% D Washington D+7 Maria Cantwell | data-sort-value="-60.5" | 60.5% D

| Cantwell58.4% D West Virginia R+20 Joe Manchin | data-sort-value="-60.6" | 60.6% D

| Manchin49.6% D Wisconsin EVEN Tammy Baldwin | data-sort-value="-51.4" | 51.4% D

| Baldwin55.4% D Wyoming R+25 John Barrasso | data-sort-value="75.7" | 75.7% R

| Barrasso67.0% R Overall | D - 43R - 489 tossups || D - 48R - 511 tossup || D - 48R - 520 tossups | D - 43R - 489 tossups || D - 45R - 505 tossups | D - 45R - 496 tossups | D - 43R - 498 tossups || D - 44R - 506 tossups || D - 45R - 505 tossups || D - 48R - 502 tossups Results:D - 47R - 53

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

2018 United States Senate elections

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