Janesville leans Republican by roughly 28 points: about 36% of voters vote Democratic and 64% Republican.
About 87% of adults in Janesville typically vote, above the U.S. average of about 62%. Among adults in Janesville, ~31% vote Democratic, ~56% Republican, and ~13% don't vote. The map below shows estimated turnout by block group.
How Janesville compares
Among cities within 25 miles, Janesville leans more Republican than 6 of 49 neighbors.
Janesville runs about 14 points more Republican than Iowa as a whole.
Politics vary noticeably by neighborhood within Janesville. The southeast side is the most Republican-leaning (R+32) and the southwest side is the least Republican-leaning (R+19), a spread of about 14 points.
Why Janesville leans the way it does
Density, race composition, education, and family structure all sit close to their national averages in Janesville. The lean here lands roughly where demographic data alone would predict.
High-school completion, uninsured rate, and voter turnout
Places that combine high-school-completion-heavy adults and a low uninsured rate tend to turn out at a higher rate, as Janesville, IA does.
Why turnout in Janesville looks the way it does
Areas with strong routine healthcare access turn out at higher rates. Janesville is in the top quarter nationally for routine-care measures such as insurance coverage, preventive screenings, and dental visits. The dental-visit rate here is about 74%, about 14 points above the U.S. average of 60%. High high-school completion lines up with higher turnout, and about 98% of adults in Janesville have completed high school, above 96% of cities. Learn more about the findings and methodology on the political spectrum map.
Nearby Cities
- Waverly, IA R+13
- North Cedar, IA R+19
- Denver, IA R+30
- Shell Rock, IA R+39
- New Hartford, IA R+40
- Cedar Falls, IA D+4
- Bremer, IA R+42
- Knittel, IA R+48
- Clarksville, IA R+46
- Horton, IA R+45
Cities with Similar Populations
- Watermill, NY D+12
- New Britain, PA D+6
- Red Hill, PA R+12
- Madelia, MN R+19
- Rancho Viejo, TX R+9
- McComb, OH R+58
- West Tawakoni, TX R+63
- Richland, PA R+50
- Reed Creek, GA R+61
- Mountainburg, AR R+64
Sources and methodology
Precinct-level voting records used to fit the model come from Iowa Secretary of State, Elections, distributed by the Voting and Election Science Team. Demographic inputs come from the U.S. Census Bureau (ACS 5-year estimates and the 2020 Decennial Census). Health and environmental inputs come from the CDC (PLACES and the Environmental Justice Index). Land cover comes from the USGS and EPA. Election-day and lead-up weather come from PRISM 4km daily grids and the NOAA Global Historical Climatology Network. Mail-voting and election-administration patterns come from the MIT Election Lab's Survey of the Performance of American Elections. Block-group crime detail comes from CrimeGrade. Internet data and modeling support provided by ISPreports.org.
Modeling and analysis by the BestNeighborhood data science team. Full methodology and findings: political spectrum map.
Methodology reviewed by the BestNeighborhood data team. Last updated May 2026.