With 4 top races, Democrats need 3 wins to gain the majority
The Wisconsin state Senate is up for grabs in 2026, for the first time since 2012. There are four seats widely seen as the top competitive races, three held by Republican incumbents and one by a Democrat.
On January 22, one of those Republicans, Rob Hutton, R-Brookfield in the 5th district, announced he will not seek reelection. State Assembly Rep. Robyn Vining, D-Wauwatosa and community advocate Sarah Harrison have announced candidacies. The State Senate Democratic Committee has endorsed Vining.
Hutton’s district in a suburban area west of Milwaukee, in eastern Waukesha county. Yes, crucial Waukesha county.
In the Senate, three Republicans hold seats that Democrat Kamala Harris won in 2024, one of those held by Hutton. No Democratic incumbent holds a seat that Republican Donald Trump won in 2024. One Democratic incumbent holds a seat that was narrowly won by Harris. These four seats are widely seen as the top races in 2026. Hutton’s retirement can only make the race for the 5th more of a Democratic pickup opportunity.
The table lists these incumbents, their districts and the 2024 presidential vote margin, as well as cash on hand as of Dec. 31st. The 2026 Wisconsin Senate races are those in odd numbered districts. These senators did not face election in 2024 in their new districts. For that reason we measure competitiveness by the presidential vote margin in 2024 and any split between the incumbent’s party and the party of the presidential winner in that new district.
In 2024, Harris won SD5 by 6 percentage points, making it easily the most lopsided of the four battleground seats. The other two split outcome Republican seats were won by Harris by just 1 point each. The Democratic held seat, the 31st, was won by Harris by 2 points. That district will pit two incumbents against one another in 2026, with Sen. Jesse James choosing to give up his quite safe 23rd district to run against Jeff Smith in the close 31st.
All past votes in this analysis are votes for statewide candidates within the current district lines. This allows comparison of voting trends since 2012 for the current district boundaries. This makes it clear that the districts designed by Democratic Gov. Tony Evers in the 2024 redistricting have put all three Republicans in newly challenging districts. The figure shows the votes for statewide races since 2012 in the new district boundaries.
In Hutton’s 5th there has been a very strong movement away from GOP majorities to moderate Democratic wins since 2020. Marklein’s new 17th district has been strongly Democratic since 2012, though with a close Harris win in 2024. Marklein brings a large war chest to the race, in which he is facing Democratic Assembly Rep. Jenna Jacobson, D-Oregon. Wanggaard’s 21st has also drifted Democratic, though not so much as the 5th. (As of Jan. 22, Wanggaard has not announced his decision on seeking reelection.) Smith’s 31st is fairly Democratic in all elections since 2016, with a somewhat close Harris win in 2024. Large liberal margins in the 2025 Supreme Court race stand out in each of the 4 districts, though that race was more lopsided statewide than any other except the 2018 U.S. Senate election.
Given the close presidential margins in the 17th and 21st, it is plausible that incumbent Republicans could hold these seats, though the past voting record in the 17th is especially challenging.
Republicans currently have an 18-15 majority in the Senate, so Democrats have to win at least three of these four races to pick up a narrow majority.