Summit leans Democratic by roughly 24 points: about 62% of voters vote Democratic and 38% Republican.
About 37% of adults in Summit typically vote, below the U.S. average of about 62%. Among adults in Summit, ~23% vote Democratic, ~14% Republican, and ~63% don't vote. The map below shows estimated turnout by block group.
How Summit compares
Among cities within 25 miles, Summit leans more Democratic than 104 of 166 neighbors.
Summit runs about 14 points more Democratic than Illinois as a whole.
Politics vary noticeably by neighborhood within Summit. The south side is the most Democratic-leaning (D+38) and the east side is the least Democratic-leaning (D+15), a spread of about 23 points.
Why Summit 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 Summit, not a ranked or complete list of what matters most.
Dense areas vote Democratic. About 98% of residents in Summit live in densely developed areas, about 62 points above the U.S. average of 36%. A high never-married share predicts Democratic voting, and about 40% of adults in Summit have never been married, above 93% of cities.
Population density and Democratic lean
Places with high population density tend to lean Democratic; Summit, IL sits in the top tenth nationally on this measure.
Why turnout in Summit looks the way it does
Areas with limited routine healthcare access turn out at lower rates. Summit is in the bottom quarter nationally for routine-care measures such as insurance coverage, preventive screenings, and dental visits. The dental-visit rate here is about 48%, about 15 points below the Illinois average of 63%. Renters vote less often than owners, and about 38% of households in Summit rent, compared to around 22% in nearby cities. High food insecurity lines up with lower turnout, and about 33% of adults in Summit report food insecurity, above 97% of cities. Learn more about the findings and methodology on the political spectrum map.
Nearby Cities
- Bedford Park, IL R+10
- McCook, IL R+17
- Forest View, IL R+14
- Lyons, IL D+14
- Stickney, IL D+16
- Hodgkins, IL R+18
- Justice, IL D+4
- Bridgeview, IL R+11
- Riverside, IL D+39
- Brookfield, IL D+23
Cities with Similar Populations
- Alpine, UT R+47
- Bonne Terre, MO R+48
- Wilkesboro, NC R+48
- Carthage, MS R+5
- Heath, TX R+45
- Wyndham, VA D+11
- Interlachen, FL R+60
- Wheelersburg, OH R+51
- Jarrell, TX R+27
- Essexville, MI R+15
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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.