Stephenson County leans slightly Republican by roughly 14 points: about 43% of voters vote Democratic and 57% Republican.
About 71% of adults in Stephenson County typically vote, above the U.S. average of about 62%. Among adults in Stephenson County, ~31% vote Democratic, ~40% Republican, and ~29% don't vote. The map below shows estimated turnout by block group.
How Stephenson County compares
Among counties within 50 miles, Stephenson County leans more Republican than 3 of 12 neighbors.
Stephenson County runs about 25 points more Republican than Illinois as a whole. Illinois leans Democratic overall, while Stephenson County is one of the few Republican-leaning pockets.
Politics vary noticeably by city within Stephenson County. The south side runs the most Democratic (D+7) and the northwest side runs the most Republican (R+46), a spread of about 53 points.
Why Stephenson County leans the way it does
This analysis examined 14,881 data points per county to find what predicts political lean and turnout. The items below are a few correlations that stood out for Stephenson County, not a ranked or complete list of what matters most.
Stephenson County votes Republican even though it is densely developed (about 49%, well above the Illinois average of 33%). Here an older population outweighs the Democratic lean that density usually predicts. Stephenson County runs against the grain of Illinois, a Republican-leaning pocket in a Democratic-leaning state.
Population density and Democratic lean
Places with high population density tend to lean Democratic; Stephenson County, IL sits in the top quarter nationally on this measure.
Why turnout in Stephenson County looks the way it does
Turnout in Stephenson County sits close to the national pattern. Routine healthcare access, homeownership, education, and food security all land near their national averages here. Learn more about the findings and methodology on the political spectrum map.
Nearby Counties
- Green County, WI R+11
- Carroll County, IL R+34
- Ogle County, IL R+28
- Winnebago County, IL D+7
- Lafayette County, WI R+31
- Jo Daviess County, IL R+18
- Lee County, IL R+21
- Rock County, WI Even
- Whiteside County, IL R+20
- Boone County, IL R+15
Counties with Similar Populations
- Phelps County, MO R+33
- Beaufort County, NC R+24
- McDowell County, NC R+50
- Warren County, MS D+6
- Bryan County, GA R+35
- Stokes County, NC R+57
- Jefferson County, PA R+55
- Barren County, KY R+50
- Henderson County, KY R+33
- Wood County, TX R+68
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Sources and methodology
Precinct-level voting records used to fit the model come from Illinois State Board of 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.