# 2018 United States Senate election in Wisconsin

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vte :
The 2018 United States Senate election in Wisconsin took place on November 6, 2018, to elect a member of the U.S. Senate from Wisconsin. This election coincided with a gubernatorial election, U.S. House elections and various other state and local elections. Incumbent Democratic senator Tammy Baldwin won re-election to a second term, defeating Republican nominee Leah Vukmir by more than 10 percentage points. This was one of ten Democratic-held Senate seats up for election in a state Donald Trump won in the 2016 presidential election. The primary elections were held on August 14, with a filing deadline on June 1. Baldwin was unopposed for the Democratic nomination, while Vukmir defeated Charles Barman, Griffin Jones, George Lucia and Kevin Nicholson in the Republican primary.

## Democratic primary
### Candidates
#### Nominee

* Tammy Baldwin, incumbent U.S. Senator

### Endorsements

U.S. Senators
* Cory Booker, U.S. Senator from New Jersey (2013-present)
* Tammy Duckworth, U.S. Senator from Illinois (2017-present)
* Dick Durbin, U.S. Senator from Illinois (1997-present), Senate Minority Whip (2015-2021)
* Russ Feingold, former U.S. Senator from Wisconsin (1993-2011)
* Al Franken, former U.S. Senator from Minnesota (2009-2018)
* Kamala Harris, U.S. Senator from California (2017-2021)
* Maggie Hassan, U.S. Senator from New Hampshire (2017-present)
* Doug Jones, U.S. Senator from Alabama (2018-2021)
* Catherine Cortez Masto, U.S. Senator from Nevada (2017-present)
* Jeff Merkley, U.S. Senator from Oregon (2009-present)
* Gary Peters, U.S. Senator from Michigan (2015-present)
* Bernie Sanders, U.S. Senator from Vermont (2007-present) (Independent)
* Elizabeth Warren, U.S. Senator from Massachusetts (2013-present)
* Sheldon Whitehouse, U.S. Senator from Rhode Island (2007-present)
Organizations
* Council for a Livable World
* Democracy for America
* EMILY's List
* End Citizens United
* J Street
* League of Conservation Voters
* LegitAction
* MoveOn.org
* National Organization for Women
* Natural Resources Defense Council
* Planned Parenthood Action Fund
* Sierra Club

### Results

Democratic primary results :
| Party | Party | Candidate | Votes | % |
| | Democratic | Tammy Baldwin (incumbent) | 510,812 | 99.64% |
| | Write-in | Write-in | 1,848 | 0.36% |
| Total votes | Total votes | Total votes | 512,660 | 100% |

## Republican primary
### Candidates
#### Nominee

* Leah Vukmir, state senator and State Senate Assistant Majority Leader

#### Eliminated in primary

* Charles Barman
* Griffin Jones
* George Lucia
* Kevin Nicholson, businessman and member of the Wisconsin Board of Veterans Affairs

#### Declined

* David Clarke, former Milwaukee County Sheriff
* Sean Duffy, U.S. Representative (running for reelection)
* Scott Fitzgerald, State Senate Majority Leader
* Mike Gallagher, U.S. Representative
* Glenn Grothman, U.S. Representative
* Eric Hovde, businessman and candidate for the U.S. Senate in 2012
* Rebecca Kleefisch, Lieutenant Governor of Wisconsin
* Dale Kooyenga, state representative
* Nicole Schneider, businesswoman
* Duey Stroebel, state senator
* Charlie Sykes, talk radio host
* Scott Walker, Governor of Wisconsin (running for reelection)

### Endorsements

Federal officials
* Steve Bannon, White House Chief Strategist (2017), executive chairman of Breitbart News
* John Bolton, 25th Ambassador to the United Nations (2005-2006)
U.S. Senators
* Ted Cruz, U.S. Senator from Texas (2013-present)
* Mike Lee, U.S. Senator from Utah (2011-present)
State legislators
* Jesse Kremer, state assemblyman from the 59th district (2015-2019)
* David Zien, state senator from the 23rd district (1993-2007)
Organizations
* Club for Growth
* FreedomWorks
* Great America PAC
* Madison Project
* Senate Conservatives Fund
* Tea Party Patriots
* Wisconsin Family Action
* Wisconsin Right to Life
Newspapers
* Kenosha News
Federal officials
* Reince Priebus, 27th White House Chief of Staff (2017)
U.S. Representatives
* Sean Duffy, U.S. Representative from Wisconsin's 7th congressional district (2011-2019)
* Glenn Grothman, U.S. Representative from Wisconsin's 6th congressional district (2015-present)
* Paul Ryan, 54th Speaker of the House (2015-2019), U.S. Representative from Wisconsin's 1st congressional district (1999-2019)
* Jim Sensenbrenner, U.S. Representative from Wisconsin's 5th congressional district (2003-2021)
State officials
* Matt Adamczyk, 35th State Treasurer of Wisconsin (2015-2019)
* Margaret Farrow, 42nd Lieutenant Governor of Wisconsin (2001-2003)
State legislators
* Scott Allen, state assemblyman from the 97th district (2015-present)
* Joan Ballweg, state assemblywoman from the 41st district (2005-2021)
* Kathy Bernier, state assemblywoman from the 68th district (2011-2019)
* Mark Born, state assemblyman from the 39th district (2013-present)
* Janel Brandtjen, state assemblyman from the 22nd district (2015-present)
* Ed Brooks, state assemblyman from the 50th district (2009-2019)
* Robert Brooks, state assemblyman from the 60th district (2015-present)
* Dave Craig, state senator from the 28th district (2017-2021)
* Alberta Darling, state senator from the 8th district (1993-2022)
* Mary Felzkowski, state assemblywoman from the 35th district (2013-2021)
* Dan Feyen, state senator from the 18th district (2017-present)
* Scott Fitzgerald, Wisconsin State Senate Majority Leader (2013-2021), state senator from the 13th district (1995-2021)
* Rick Gundrum, state assemblyman from the 58th district (2018-present)
* Cody Horlacher, state assemblyman from the 33rd district (2015-2023)
* André Jacque, state assemblyman from the 2nd district (2011-2019)
* John Jagler, state assemblyman from the 37th district (2013-2021)
* Adam M. Jarchow, state assemblyman from the 28th district (2015-2019)
* Dan Kapanke, state senator from the 32nd district (2005-2011)
* Terry Katsma, state assemblyman from the 26th district (2015-present)
* Samantha Kerkman, state assemblywoman from the 61st district (2013-2022)
* Joel Kitchens, state assemblyman from the 1st district (2015-present)
* Joel Kleefisch, state assemblyman from the 38th district (2005-2019)
* Dan Knodl, state assemblyman from the 24th district (2009-present)
* Dean Knudson, state assemblyman from the 30th district (2011-2017)
* Scott Krug, state assemblyman from the 72nd district (2011-present)
* Mike Kuglitsch, state assemblyman from the 84th district (2011-2022)
* Bob Kulp, state assemblyman from the 69th district (2013-2021)
* Mary Lazich, Wisconsin Senate President (2015-2017), state senator from the 28th district (1998-2017)
* Devin LeMahieu, state senator from the 9th district (2015-present)
* Amy Loudenbeck, state assemblywoman from the 31st district (2013-2023), 45th district (2011-2013)
* John Macco, state assemblyman from the 88th district (2015-present)
* Howard Marklein, Wisconsin Senate President Pro Tempore (2017-2021), state senator from the 17th district (2015-present)
* Dave Murphy, state assemblyman from the 56th district (2013-present)
* Stephen Nass, state senator from the 11th district (2015-present)
* Adam Neylon, state senator from the 98th district (2013-present)
* John Nygren, state assemblyman from the 89th district (2007-2020)
* Luther Olsen, state senator from the 14th district (2005-2021)
* Jim Ott, state assemblyman from the 23rd district (2007-2021)
* Jerry Petrowski, state senator from the 29th district (2012-present)
* Treig Pronschinske, state assemblyman from the 92nd district (2017-present)
* Romaine Quinn, state assemblywoman from the 75th district (2015-2021)
* Mike Rohrkaste, state assemblyman from the 55th district (2015-2021)
* Roger Roth, Wisconsin Senate President (2017-2021), state senator from the 19th district (2015-present)
* Joe Sanfelippo, state assemblyman from the 15th district (2013-2023)
* Michael Schraa, state assemblyman from the 53rd district (2013-present)
* Ken Skowronski, state assemblyman from the 82nd district (2014-2023)
* Patrick Snyder, state assemblyman from the 85th district (2017-present)
* John Spiros, state assemblyman from the 86th district (2013-present)
* Rob Stafsholt, state assemblyman from the 29th district (2017-2021)
* David Steffen, state assemblyman from the 4th district (2015-present)
* Jim Steineke, Wisconsin Assembly Majority Leader (2015-2022), state assemblyman from the 5th district (2011-2022)
* Duey Stroebel, state senator from the 20th district (2015-present)
* Rob Swearingen, state assemblyman from the 34th district (2013-present)
* Gary Tauchen, state assemblyman from the 6th district (2007-2023)
* Patrick Testin, state senator from the 24th district (2017-present)
* Jeremy Thiesfeldt, state assemblyman from the 52nd district (2011-2023)
* Travis Tranel, state assemblyman from the 49th district (2011-present)
* Van Wanggaard, state senator from the 21st district (2015-present)
* Tom Weatherston, state assemblyman from the 62nd district (2013-2019)
* Chuck Wichgers, state assemblyman from the 83rd district (2017-2023)
* Shannon Zimmerman, state assemblyman from the 30th district (2017-present)
Local officials
* Dave Ament, Mayor of New Berlin
* David Beth, Kenosha County Sheriff
* Christopher Bossert, Washington County Supervisor
* John Bulawa, Washington County Supervisor
* Michael Crowley, Waukesha County Supervisor
* Paul Decker, Waukesha County Board Chairman
* Paul Farrow, Waukesha County Executive (2015-present)
* Tyson Fettes, Racine County Register of Deeds
* Adam Gerol, Ozaukee County District Attorney
* Tricia Hanson, Racine County District Attorney
* Darlene Johnson, Waukesha County Supervisor
* Bob Long, St. Croix County Supervisor
* Travis Nez, former Price County Supervisor
* Michael Nieskes, St. Croix County District Attorney
* Harley Raebe, Green Lake County Supervisor
* Dale Schmidt, Dodge County Sheriff
* Dan Sebring, Milwaukee County Supervisor
* Lawrence Smith, Winnebago County Supervisor
* Peter Sorce, Washington County Supervisor
* John Spears, Vernon County Sheriff
* Daniel P. Vrakas, Waukesha County Executive (2005-2015)
* Chuck Wood, Waukesha County Supervisor
* Fred Zaug, Waupaca County Supervisor
* David Zimmerman, Waukesha County Supervisor
Individuals
* Rachel Campos-Duffy, television personality
* Michael W. Grebe, philanthropist, lawyer, businessman and conservative activist
* John C. McAdams, professor at Marquette University
* Kevin Nicholson, veteran and former 2018 Senate candidate
* Tonette Walker, First Lady of Wisconsin (2011-2019)
* Jay Weber, WISN-AM talk show host
Organizations
* Maggie's List
* NRA Political Victory Fund
* Republican Party of Wisconsin
* RightNOW Women
* Wisconsin Family Action
* Wisconsin Right to Life
* Wisconsin Young Republicans

### Polling

| Poll source | Date(s) administered | Sample size | Margin of error | Kevin Nicholson | Leah Vukmir | Other | Undecided |
| Emerson College | July 26–28, 2018 | 238 | ± 6.5% | 35% | 35% | 3% | 27% |
| Marist College | July 15–19, 2018 | 355 | ± 6.1% | 38% | 28% | <1% | 34% |
| Hodas & Associates (R-Restoration PAC) | July 12–16, 2018 | 600 | ± 3.0% | 33% | 20% | – | 47% |
| Marquette University | July 11–15, 2018 | 266 | ± 7.0% | 32% | 34% | 2% | 30% |
| Marquette University | June 13–17, 2018 | 274 | ± 6.9% | 37% | 32% | 1% | 30% |
| Hodas & Associates (R-Restoration PAC) | June 7–12, 2018 | 600 | ± 3.0% | 28% | 14% | – | 58% |
| The Tarrance Group (R-Wisconsin Next PAC) | May 31 – June 4, 2018 | 800 | ± 3.5% | 29% | 36% | – | 35% |
| American Viewpoint (R-Vukmir) | May 29–31, 2018 | 500 | ± 4.4% | 32% | 30% | – | – |
| Hodas & Associates (R-Restoration PAC) | April 30 – May 3, 2018 | 240 | ± 6.0% | 46% | 15% | – | – |
| WPA Intelligence (R-Nicholson) | April 2–4, 2018 | 1,028 | ± 3.1% | 45% | 27% | – | 28% |
| Marquette University | February 25 – March 1, 2018 | 243 | ± 8.2% | 28% | 19% | 2% | 49% |
| WPA Intelligence (R-Nicholson) | January 22–23, 2018 | 350 | ± 5.2% | 48% | 9% | 1% | 42% |
| WPA Intelligence (R-Nicholson) | January 2–3, 2018 | 350 | ± 5.2% | 27% | 10% | 2% | 60% |
| WPA Intelligence (R-Nicholson) | December 6–7, 2017 | 1,004 | ± 3.1% | 30% | 23% | 2% | 45% |

#### Notes

* ↑ John Schiess 1%
* 1 2 John Schiess 2%
| Poll source | Date(s) administered | Sample size | Margin of error | David Clarke | Sean Duffy | Undecided |
| Magellan Strategies (R) | February 15–16, 2017 | 300 | ± 5.7% | 32% | 26% | 42% |

#### Results

Republican primary results :
| Party | Party | Candidate | Votes | % |
| | Republican | Leah Vukmir | 217,230 | 48.90% |
| | Republican | Kevin Nicholson | 191,276 | 43.06% |
| | Republican | George Lucia | 18,786 | 4.23% |
| | Republican | Griffin Jones | 8,699 | 1.96% |
| | Republican | Charles Barman | 7,959 | 1.79% |
| | Write-in | Write-in | 303 | 0.07% |
| Total votes | Total votes | Total votes | 444,253 | 100% |

## General election
### Endorsements

U.S. Executive Branch officials
* Mike Pence, 48th Vice President of the United States (2017-2021)
* Reince Priebus, 27th White House Chief of Staff (2017)
* Condoleezza Rice, 66th United States Secretary of State (2005-2009)
* Donald Trump, 45th President of the United States (2017-2021)
U.S. Senators
* Ron Johnson, U.S. Senator from Wisconsin (2011-present)
U.S. Representatives
* Sean Duffy, U.S. Representative from Wisconsin's 7th congressional district (2011-2019)
* Glenn Grothman, U.S. Representative from Wisconsin's 6th congressional district (2015-present)
* Paul Ryan, 54th Speaker of the House of Representatives (2015-2019), U.S. Representative from Wisconsin's 1st congressional district (1999-2019)
* Jim Sensenbrenner, U.S. Representative from Wisconsin's 5th congressional district (2003-2021)
State officials
* Matt Adamczyk, 35th State Treasurer of Wisconsin (2015-2019)
* Margaret Farrow, 42nd Lieutenant Governor of Wisconsin (2001-2003)
State legislators
* Scott Allen, state assemblyman from the 97th district (2015-present)
* Joan Ballweg, state assemblywoman from the 41st district (2005-2021)
* Kathy Bernier, state assemblywoman from the 68th district (2011-2019)
* Mark Born, state assemblyman from the 39th district (2013-present)
* Janel Brandtjen, state assemblyman from the 22nd district (2015-present)
* Ed Brooks, state assemblyman from the 50th district (2009-2019)
* Robert Brooks, state assemblyman from the 60th district (2015-present)
* Dave Craig, state senator from the 28th district (2017-2021)
* Alberta Darling, state senator from the 8th district (1993-2022)
* Mary Felzkowski, state assemblywoman from the 35th district (2013-2021)
* Dan Feyen, state senator from the 18th district (2017-present)
* Scott Fitzgerald, Wisconsin State Senate Majority Leader (2013-2021), state senator from the 13th district (1995-2021)
* Rick Gundrum, state assemblyman from the 58th district (2018-present)
* Cody Horlacher, state assemblyman from the 33rd district (2015-2023)
* André Jacque, state assemblyman from the 2nd district (2011-2019)
* John Jagler, state assemblyman from the 37th district (2013-2021)
* Adam M. Jarchow, state assemblyman from the 28th district (2015-2019)
* Dan Kapanke, state senator from the 32nd district (2005-2011)
* Terry Katsma, state assemblyman from the 26th district (2015-present)
* Samantha Kerkman, state assemblywoman from the 61st district (2013-2022)
* Joel Kitchens, state assemblyman from the 1st district (2015-present)
* Joel Kleefisch, state assemblyman from the 38th district (2005-2019)
* Dan Knodl, state assemblyman from the 24th district (2009-2023)
* Dean Knudson, state assemblyman from the 30th district (2011-2017)
* Scott Krug, state assemblyman from the 72nd district (2011-present)
* Mike Kuglitsch, state assemblyman from the 84th district (2011-2022)
* Bob Kulp, state assemblyman from the 69th district (2013-2021)
* Mary Lazich, Wisconsin Senate President (2015-2017), state senator from the 28th district (1998-2017)
* Devin LeMahieu, state senator from the 9th district (2015-present)
* Amy Loudenbeck, state assemblywoman from the 31st district (2013-2023), 45th district (2011-2013)
* John Macco, state assemblyman from the 88th district (2015-present)
* Howard Marklein, Wisconsin Senate President Pro Tempore (2017-2021), state senator from the 17th district (2015-present)
* Dave Murphy, state assemblyman from the 56th district (2013-present)
* Stephen Nass, state senator from the 11th district (2015-present)
* Adam Neylon, state senator from the 98th district (2013-present)
* John Nygren, state assemblyman from the 89th district (2007-2020)
* Luther Olsen, state senator from the 14th district (2005-2021)
* Jim Ott, state assemblyman from the 23rd district (2007-2021)
* Jerry Petrowski, state senator from the 29th district (2012-present)
* Treig Pronschinske, state assemblyman from the 92nd district (2017-present)
* Romaine Quinn, state assemblywoman from the 75th district (2015-2021)
* Mike Rohrkaste, state assemblyman from the 55th district (2015-2021)
* Roger Roth, Wisconsin Senate President (2017-2021), state senator from the 19th district (2015-2023)
* Joe Sanfelippo, state assemblyman from the 15th district (2013-2023)
* Michael Schraa, state assemblyman from the 53rd district (2013-present)
* Ken Skowronski, state assemblyman from the 82nd district (2014-2023)
* Patrick Snyder, state assemblyman from the 85th district (2017-present)
* John Spiros, state assemblyman from the 86th district (2013-present)
* Rob Stafsholt, state assemblyman from the 29th district (2017-2021)
* David Steffen, state assemblyman from the 4th district (2015-present)
* Jim Steineke, Wisconsin Assembly Majority Leader (2015-2022), state assemblyman from the 5th district (2011-2022)
* Duey Stroebel, state senator from the 20th district (2015-present)
* Rob Swearingen, state assemblyman from the 34th district (2013-present)
* Gary Tauchen, state assemblyman from the 6th district (2007-2023)
* Patrick Testin, state senator from the 24th district (2017-present)
* Jeremy Thiesfeldt, state assemblyman from the 52nd district (2011-2023)
* Travis Tranel, state assemblyman from the 49th district (2011-present)
* Van Wanggaard, state senator from the 21st district (2015-present)
* Tom Weatherston, state assemblyman from the 62nd district (2013-2019)
* Chuck Wichgers, state assemblyman from the 83rd district (2017-2023)
* Shannon Zimmerman, state assemblyman from the 30th district (2017-present)
Local officials
* Dave Ament, Mayor of New Berlin
* David Beth, Kenosha County Sheriff
* Christopher Bossert, Washington County Supervisor
* John Bulawa, Washington County Supervisor
* Michael Crowley, Waukesha County Supervisor
* Paul Decker, Waukesha County Board Chairman
* Paul Farrow, Waukesha County Executive (2015-present)
* Tyson Fettes, Racine County Register of Deeds
* Adam Gerol, Ozaukee County District Attorney
* Tricia Hanson, Racine County District Attorney
* Darlene Johnson, Waukesha County Supervisor
* Bob Long, St. Croix County Supervisor
* Travis Nez, former Price County Supervisor
* Michael Nieskes, Racine County District Attorney
* Harley Raebe, Green Lake County Supervisor
* Dale Schmidt, Dodge County Sheriff
* Dan Sebring, Milwaukee County Supervisor
* Lawrence Smith, Winnebago County Supervisor
* Peter Sorce, Washington County Supervisor
* John Spears, Vernon County Sheriff
* Daniel P. Vrakas, Waukesha County Executive (2005-2015)
* Chuck Wood, Waukesha County Supervisor
* Fred Zaug, Waupaca County Supervisor
* David Zimmerman, Waukesha County Supervisor
Individuals
* Rachel Campos-Duffy, television personality
* Michael W. Grebe, philanthropist, lawyer, businessman and conservative activist
* John C. McAdams, professor at Marquette University
* Eric Trump, businessman and son of U.S. President Donald Trump
* Tonette Walker, First Lady of Wisconsin (2011-2019)
* Jay Weber, WISN-AM talk show host
Organizations
* Maggie's List
* Milwaukee Police Association
* NRA Political Victory Fund
* Republican Party of Wisconsin
* RightNOW Women
* U.S. Chamber of Commerce
* Wisconsin Family Action
* Wisconsin Right to Life
* Wisconsin Young Republicans
Former U.S. Executive Branch officials
* Joe Biden, 47th Vice President of the United States (2009-2017)
* Barack Obama, 44th President of the United States (2009-2017)
U.S. Senators
* Cory Booker, U.S. Senator from New Jersey (2013-present)
* Tammy Duckworth, U.S. Senator from Illinois (2017-present)
* Dick Durbin, U.S. Senator from Illinois (1997-present), Senate Minority Whip (2015-2021)
* Russ Feingold, U.S. Senator from Wisconsin (1993-2011)
* Al Franken, U.S. Senator from Minnesota (2009-2018)
* Kamala Harris, U.S. Senator from California (2017-2021)
* Maggie Hassan, U.S. Senator from New Hampshire (2017-present)
* Doug Jones, U.S. Senator from Alabama (2018-2021)
* Catherine Cortez Masto, U.S. Senator from Nevada (2017-present)
* Jeff Merkley, U.S. Senator from Oregon (2009-present)
* Gary Peters, U.S. Senator from Michigan (2015-present)
* Bernie Sanders, U.S. Senator from Vermont (2007-present) (Independent)
* Elizabeth Warren, U.S. Senator from Massachusetts (2013-present)
* Sheldon Whitehouse, U.S. Senator from Rhode Island (2007-present)
U.S. Representatives
* Joe Kennedy III, U.S. Representative from Massachusetts's 4th congressional district (2013-2021)
* Gwen Moore, U.S. Representative from Wisconsin's 4th congressional district (2005-present)
* Mark Pocan, U.S. Representative from Wisconsin's 2nd congressional district (2013-present)
State officials
* Tony Evers, 26th Wisconsin Superintendent of Public Instruction (2009-2019) and nominee for Governor of Wisconsin in 2018
State legislators
* Mandela Barnes, state assemblyman from the 11th district (2013-2017) and nominee for Lieutenant Governor of Wisconsin in 2018
Local officials
* Bill de Blasio, 109th Mayor of New York City (2014-2021)
Individuals
* Stephanie Schriock, political strategist
* Amy Siskind, activist and writer
* Bradley Whitford, actor and activist
Organizations
* Alliance for Retired Americans
* Council for a Livable World
* Democracy for America
* EMILY's List
* End Citizens United
* Feminist Majority Political Action Committee
* J Street
* League of Conservation Voters
* LegitAction
* MoveOn.org
* National Committee to Preserve Social Security and Medicare
* National Organization for Women
* Natural Resources Defense Council
* Planned Parenthood Action Fund
* Population Connection
* Rachel's Action Network
* Run with Pride
* Sierra Club
* United Automobile Workers

### Debates

* Complete video of debate, October 8, 2018
* Complete video of debate, October 13, 2018

### Predictions

| Source | Ranking | As of |
| The Cook Political Report | Likely D | October 26, 2018 |
| Inside Elections | Safe D | November 1, 2018 |
| Sabato's Crystal Ball | Likely D | November 5, 2018 |
| Fox News | Likely D | November 5, 2018 |
| CNN | Likely D | November 5, 2018 |
| RealClearPolitics | Lean D | November 5, 2018 |

#### Notes

* ↑ The Fox News Midterm Power Rankings uniquely does not contain a category for Safe/Solid races

### Polling

| Poll source | Date(s) administered | Sample size | Margin of error | Tammy Baldwin (D) | Leah Vukmir (R) | Other | Undecided |
| Research Co. | November 1–3, 2018 | 450 | ± 4.6% | 50% | 39% | – | 11% |
| Emerson College | October 29–31, 2018 | 604 | ± 4.1% | 53% | 44% | – | 3% |
| Marquette University | October 24–28, 2018 | 1,154 LV | ± 3.2% | 54% | 43% | – | 1% |
| Marquette University | October 24–28, 2018 | 1,400 RV | ± 3.0% | 52% | 42% | – | 3% |
| Ipsos | October 12–18, 2018 | 1,193 | ± 3.0% | 54% | 39% | 3% | 5% |
| Public Policy Polling (D-Protect Our Care) | October 10–11, 2018 | 816 | ± 3.4% | 52% | 42% | – | 6% |
| Marquette University | October 3–7, 2018 | 799 LV | ± 3.9% | 53% | 43% | – | 2% |
| Marquette University | October 3–7, 2018 | 1,000 RV | ± 3.6% | 53% | 42% | – | 3% |
| Marist College | September 30 – October 3, 2018 | 571 LV | ± 4.8% | 54% | 40% | 1% | 5% |
| Marist College | September 30 – October 3, 2018 | 781 RV | ± 4.1% | 53% | 40% | 1% | 6% |
| Ipsos | September 14–24, 2018 | 1,109 | ± 3.0% | 52% | 39% | 4% | 5% |
| Marquette University | September 12–16, 2018 | 614 LV | ± 4.4% | 53% | 42% | – | 2% |
| Marquette University | September 12–16, 2018 | 800 RV | ± 4.0% | 52% | 40% | – | 4% |
| Suffolk University | August 18–24, 2018 | 500 | ± 4.4% | 50% | 42% | – | 8% |
| Marquette University | August 15–19, 2018 | 601 LV | ± 4.5% | 49% | 47% | – | 2% |
| Marquette University | August 15–19, 2018 | 800 RV | ± 4.0% | 51% | 43% | – | 4% |
| Emerson College | July 26–28, 2018 | 632 | ± 4.2% | 50% | 36% | 4% | 10% |
| Marist College | July 15–19, 2018 | 906 | ± 3.8% | 55% | 38% | 1% | 6% |
| SurveyMonkey/Axios | June 11 – July 2, 2018 | 968 | ± 4.5% | 56% | 40% | – | 4% |
| Marquette University | June 13–17, 2018 | 800 | ± 4.0% | 49% | 40% | – | 8% |
| Public Policy Polling (D-Protect Our Care) | March 15–16, 2018 | 910 | ± 3.3% | 51% | 39% | – | 10% |
with Kevin Nicholson
| Poll source | Date(s) administered | Sample size | Margin of error | Tammy Baldwin (D) | Kevin Nicholson (R) | Other | Undecided |
| Emerson College | July 26–28, 2018 | 632 | ± 4.2% | 49% | 40% | 3% | 9% |
| Marist College | July 15–19, 2018 | 906 | ± 3.8% | 54% | 39% | 1% | 6% |
| SurveyMonkey/Axios | June 11 – July 2, 2018 | 968 | ± 4.5% | 55% | 42% | – | 3% |
| Marquette University | June 13–17, 2018 | 800 | ± 4.0% | 50% | 39% | – | 7% |
| Public Policy Polling (D-Protect Our Care) | March 15–16, 2018 | 910 | ± 3.3% | 51% | 38% | – | 11% |
with generic Republican
| Poll source | Date(s) administered | Sample size | Margin of error | Tammy Baldwin (D) | Generic Republican | Undecided |
| SurveyMonkey/Axios | February 12 – March 5, 2018 | 1,668 | ± 3.6% | 49% | 46% | 5% |
with David Clarke
| Poll source | Date(s) administered | Sample size | Margin of error | Tammy Baldwin (D) | David Clarke (R) | Other | Undecided |
| Magellan Strategies (R) | February 9–10, 2017 | 500 | ± 4.4% | 49% | 35% | 2% | 14% |
with Sean Duffy
| Poll source | Date(s) administered | Sample size | Margin of error | Tammy Baldwin (D) | Sean Duffy (R) | Other | Undecided |
| Magellan Strategies (R) | February 9–10, 2017 | 500 | ± 4.4% | 49% | 36% | 2% | 13% |

### Results

Despite initial expectations of a potentially close race, Baldwin ended up winning by over 10 percentage points, which was the highest margin of victory for a Wisconsin Democratic statewide candidate in 2018. She ran up the margins in the traditional Democratic strongholds of Milwaukee and Madison, but also won in western Wisconsin, Green Bay and most of the counties bordering Illinois, including Racine, Rock, and Kenosha counties. This is the largest margin of victory for the Democrats in a major Wisconsin statewide campaign (presidential, senate, gubernatorial) since 2008.
United States Senate election in Wisconsin, 2018 :
| Party | Party | Candidate | Votes | % | ±% |
| | Democratic | Tammy Baldwin (incumbent) | 1,472,914 | 55.36% | +3.95% |
| | Republican | Leah Vukmir | 1,184,885 | 44.53% | −1.33% |
| | Write-in | Write-in | 2,964 | 0.11% | N/A |
| Total votes | Total votes | Total votes | 2,660,763 | 100.00% | N/A |
| | Democratic hold | Democratic hold | Democratic hold | Democratic hold | Democratic hold |

#### Counties that flipped from Democratic to Republican

* Buffalo (largest city: Mondovi)
* Forest (largest city: Crandon)
* Juneau (largest city: Mauston)
* Lincoln (largest city: Merrill)
* Pepin (largest city: Durand)
* Price (largest city: Park Falls)
* Sawyer (largest city: Hayward)
* Chippewa (largest city: Chippewa Falls)
* Wood (largest city: Marshfield)

#### Counties that flipped from Republican to Democratic

* Outagamie (largest city: Appleton)
* Brown (largest city: Green Bay)

#### By congressional district

As a result of partisan gerrymandering, Baldwin only won 3 out of the state's 8 Congressional districts, despite winning the election comfortably by over 10 percentage points.
| District | Baldwin | Vukmir | Representative |
| 1st | 49.6% | 50.3% | Bryan Steil |
| 2nd | 73.4% | 26.4% | Mark Pocan |
| 3rd | 56.4% | 43.5% | Ron Kind |
| 4th | 78.6% | 21.3% | Gwen Moore |
| 5th | 43.0% | 56.9% | Jim Sensenbrenner |
| 6th | 47.5% | 52.4% | Glenn Grothman |
| 7th | 47.7% | 52.2% | Sean Duffy |
| 8th | 48.5% | 51.5% | Mike Gallagher |