99chambers

Wisconsin State Senate seat · lines in effect since 2024

Wisconsin Senate District 15

A district of about 175,000 people, 26% of adults with a bachelor's degree. It votes D+8.9 relative to the nation for president.

Mark Spreitzer (D) · since Nov 8, 2022Next election Nov 5, 2030The 2026 race →

Where it sits among all 33 seats

Every Wisconsin State Senate seat by partisan lean, from most Democratic to most Republican. Lean is the seat's presidential vote on current lines, relative to the nation.

D+8.98th most
Democratic
Most DemocraticMost Republican17th seat · the majority lineDistrict 15

Source: 99chambers: 2024 and 2020 presidential results on current lines, relative to the nation (2024 weighted 3:1)Updated Oct 16, 2026, 5:19 AM ET

Every race on these lines

Results recomputed from precinct returns as if today's boundaries had always existed, so years compare like for like.

20242026
U.S. SenateD+10.6No race
Wisconsin State SenateNo raceD+19.4

Outlined: the race for this seat itselfBlank: no race that year

Source: 99chambers results archive: precinct results allocated to current lines; 2026: civicAPIUpdated Nov 7, 2026, 3:01 PM ET

Who lives here, compared

Grey bars show the spread of all 33 seats. Small marks are other seats in Wisconsin. The black marker is District 15.

Adults with a bachelor's degree26% 19th pct · 27th of 33 in WI

Lower than 81% of seats.

White adults without a degree61% 53rd pct · 16th of 33 in WI

Higher than 53% of seats.

Hispanic residents10% 84th pct · 6th of 33 in WI

Higher than 84% of seats.

Black residents4% 75th pct · 9th of 33 in WI

Higher than 75% of seats.

Asian residents1% 28th pct · 24th of 33 in WI

Lower than 72% of seats.

People per square mile233 50th pct · 17th of 33 in WI

Denser than 50% of seats.

Source: Census Bureau, American Community Survey 2020–2024 5-year estimates, allocated to current linesUpdated Oct 13, 2026, 5:06 AM ET

Seats most like this one

Nearest seats on demographics, density and lean. 1 of the 4 flipped this year.

District 14
27% college gradsD+2.3Not up in 2026District 17
29% college gradsD+2.4Flipped DDistrict 32
32% college gradsD+3.6Not up in 2026District 31
33% college gradsD+3.2Held D

Source: Census Bureau, American Community Survey 2020–2024 5-year estimates, allocated to current lines; 99chambers: 2024 and 2020 presidential results on current lines, relative to the nation (2024 weighted 3:1)Updated Oct 16, 2026, 5:19 AM ET

Who has held it

These lines took effect in 2024.

  1. Mark Spreitzer (D)
    2027– · Won 2026 by 19.4

Source: Past results: 99chambers results archive (MEDSL, Klarner, state election offices)