South Jacksonville leans Republican by roughly 22 points: about 39% of voters vote Democratic and 61% Republican.
About 74% of adults in South Jacksonville typically vote, above the U.S. average of about 62%. Among adults in South Jacksonville, ~29% vote Democratic, ~45% Republican, and ~26% don't vote. The map below shows estimated turnout by block group.
How South Jacksonville compares
Among cities within 25 miles, South Jacksonville leans more Republican than 2 of 56 neighbors.
South Jacksonville runs about 32 points more Republican than Illinois as a whole. Illinois leans Democratic overall, while South Jacksonville is one of the few Republican-leaning pockets.
Politics vary noticeably by neighborhood within South Jacksonville. The southwest side is the most Republican-leaning (R+30) and the northwest side is the least Republican-leaning (R+14), a spread of about 16 points.
Why South Jacksonville leans the way it does
This analysis examined 14,881 data points per city to find what predicts political lean and turnout. The items below are a few correlations that stood out for South Jacksonville, not a ranked or complete list of what matters most.
South Jacksonville votes Republican even though it is densely developed (about 55%, well above the Illinois average of 33%). State and regional patterns outweigh the Democratic lean that density usually predicts here. South Jacksonville runs against the grain of Illinois, a Republican-leaning pocket in a Democratic-leaning state.
Developed land and Democratic lean
Places with a heavily developed built environment tend to lean Democratic; South Jacksonville, IL sits in the top quarter nationally on this measure. Developed land does not change how people vote; it mostly reflects how urban a place is.
Why turnout in South Jacksonville looks the way it does
Turnout in South Jacksonville 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 Cities
- Jacksonville, IL R+13
- Arnold, IL R+52
- Pisgah, IL R+55
- Woodson, IL R+54
- Lynnville, IL R+50
- Sinclair, IL R+50
- Murrayville, IL R+55
- Merritt, IL R+61
- Alexander, IL R+54
- Literberry, IL R+49
Cities with Similar Populations
- Myrtle, MS R+79
- Hampton, SC R+5
- Robins, IA R+6
- Brandon, VT R+19
- Germanton, NC R+56
- Mount Bethel, PA R+31
- Mooreville, MS R+76
- Dunean, SC D+17
- Monroe, IN R+72
- Scotts, MI R+19
All Local Stats
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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.