2018 United States Senate election in Wisconsin

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 [2018 United States House of Representatives 2018 United States House of Representatives elections in Wisconsin|elections in Wisconsin|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

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
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

Polling

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

General election

Debates

, October 8, 2018
, October 13, 2018

Polling

Poll source	Date administered	Sample size	Margin of error	Tammy Baldwin	Leah Vukmir	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 administered	Sample size	Margin of error	Tammy Baldwin	Kevin Nicholson	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 administered	Sample size	Margin of error	Tammy Baldwin	Generic Republican	Undecided
SurveyMonkey/Axios	February 12 – March 5, 2018	1,668	± 3.6%	49%	46%	5%

with David Clarke

Poll source	Date administered	Sample size	Margin of error	Tammy Baldwin	David Clarke	Other	Undecided
Magellan Strategies (R)	February 9–10, 2017	500	± 4.4%	49%	35%	2%	14%

with Sean Duffy

Poll source	Date administered	Sample size	Margin of error	Tammy Baldwin	Sean Duffy	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 was the largest margin of victory for the Democrats in a major Wisconsin statewide campaign since 2008.

Counties that flipped from Democratic to Republican

Counties that flipped from Republican to Democratic

By congressional district

As a result of partisan gerrymandering, Baldwin only won three out of the state's eight Congressional districts, despite winning the election comfortably by over ten percentage points.

District	Baldwin	Vukmir	Representative
	49.6%	50.3%	Bryan Steil
	73%	26%	Mark Pocan
	56%	44%	Ron Kind
	79%	21%	Gwen Moore
	43%	57%	Jim Sensenbrenner
	47%	52%	Glenn Grothman
	48%	52%	Sean Duffy
	48%	51%	Mike Gallagher