| Election Name: | Washington State Senate elections, 2018 |
| Country: | Washington |
| Type: | legislative |
| Ongoing: | no |
| Previous Election: | 2016 Washington State Senate election |
| Previous Year: | 2016 |
| Next Election: | 2020 Washington State Senate election |
| Next Year: | 2020 |
| Seats For Election: | 25 of 49 seats in the Washington State Senate |
| Majority Seats: | 25 |
| Election Date: | November 6, 2018 |
| Image1: | Sharon Nelson 01B.jpg |
| Leader1: | Sharon Nelson |
| Party1: | Washington Democratic Party |
| Leaders Seat1: | 33rd-Des Moines |
| Last Election1: | 24 |
| Seats Before1: | 25 |
| Seats1: | 28 |
| Seat Change1: | 3 |
| Popular Vote1: | 982,741 |
| Percentage1: | 64.55% |
| Swing1: | 18.73 pp |
| Leader2: | Mark Schoesler |
| Party2: | Washington Republican Party |
| Leaders Seat2: | 9th-Ritzville |
| Last Election2: | 25 |
| Seats Before2: | 24 |
| Seats2: | 21 |
| Seat Change2: | 3 |
| Popular Vote2: | 516,476 |
| Percentage2: | 33.92% |
| Swing2: | 16.94 pp |
| Map Size: | 350px |
| President pro tempore | |
| Before Party: | Democratic |
| After Election: | Karen Keiser |
| After Party: | Democratic |
The 2018 Washington State Senate elections took place as part of the biennial United States elections. Washington state voters elected state senators in 25 of the state's 49 Senate districts. The other 24 state senators were not up for re-election until the next biennial election in 2020. State senators serve four-year terms in the Washington State Senate. A statewide map of Washington's state legislative districts is provided by the Washington State Legislature here, .
A top two primary election on August 7, 2018, determined which candidates appear on the November 6 general election ballot. Each candidate is allowed to write in their party preference so that it appears as they desire on the ballot.[1]
Following the 2016 state senate elections, Republicans maintained effective control of the Senate, 25–24 because self-identified Democrat Tim Sheldon caucuses with the Republicans. However, in 2017 Democrats regained control of the Washington State Senate after Democrat Manka Dhingra won a special election in Washington's 45th legislative district.
Democrats expanded their caucus's majority to 28–21 by further flipping the 26th, 30th, and 47th districts. Tim Sheldon was reelected as a Democrat, but continued to caucus with the Republicans.
| 2018 Washington State Senate electionPrimary election — August 7, 2018 | |||||||
|---|---|---|---|---|---|---|---|
| Party | Votes | Percentage | Candidates | Advancing to general | Seats contesting | ||
| Democratic | 536,781 | 61.87% | 37 | 28 | 24 | ||
| Republican | 302,667 | 34.89% | 26 | 19 | 19 | ||
| Independent | 15,375 | 1.77% | 6 | 1 | 1 | ||
| Libertarian | 9,998 | 1.15% | 4 | 1 | 1 | ||
| No party preference | 2,737 | 0.32% | 2 | 0 | 0 | ||
| Totals | 2,869,914 | 100.00% | 75 | 49 | — | ||
| 2018 Washington State Senate electionGeneral election — November 6, 2018 | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Party | Votes | Percentage | Not up | Contested | Before | After | +/– | ||
| Democratic | 982,741 | 64.55% | 10 | 7 | 25 | 28 | 3 | ||
| Republican | 516,476 | 33.92% | 12 | 11 | 24 | 21 | 3 | ||
| Independent | 13,538 | 0.89% | 0 | 0 | 0 | 0 | 0 | ||
| Libertarian | 9,707 | 0.64% | 0 | 0 | 0 | 0 | 0 | ||
| Totals | 1,522,462 | 100.00% | 24 | 25 | 49 | 49 | — | ||
*Tim Sheldon self-identifies as a Democrat but caucuses with the Republicans.Source:[2]