Peoria County leans slightly Democratic by roughly 14 points: about 57% of voters vote Democratic and 43% Republican.
About 71% of adults in Peoria County typically vote, above the U.S. average of about 62%. Among adults in Peoria County, ~40% vote Democratic, ~31% Republican, and ~29% don't vote. The map below shows estimated turnout by block group.
How Peoria County compares
Among counties within 50 miles, Peoria County is the most Democratic-leaning.
Politically, Peoria County sits close to the rest of Illinois.
Politics vary noticeably by city within Peoria County. The southeast side runs the most Democratic (D+59) and the northwest side runs the most Republican (R+28), a spread of about 87 points.
Why Peoria 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 Peoria County, not a ranked or complete list of what matters most.
Dense areas vote Democratic. About 66% of residents in Peoria County live in densely developed areas, about 30 points above the U.S. average of 36%. High college attainment predicts Democratic voting, and Peoria County sits in the top quarter (about 35%, above 86% of counties). A high never-married share predicts Democratic voting, and about 36% of adults in Peoria County have never been married, above 86% of counties.
Population density and Democratic lean
Places with high population density tend to lean Democratic; Peoria County, IL sits in the top quarter nationally on this measure.
Why turnout in Peoria County looks the way it does
Turnout in Peoria 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
- Tazewell County, IL R+29
- Woodford County, IL R+40
- Stark County, IL R+47
- Marshall County, IL R+37
- Fulton County, IL R+31
- Mason County, IL R+46
- Knox County, IL R+9
- Putnam County, IL R+28
- McLean County, IL D+5
- Logan County, IL R+41
Counties with Similar Populations
- Ulster County, NY D+16
- Kent County, DE D+5
- Shasta County, CA R+30
- Medina County, OH R+25
- Kanawha County, WV R+19
- Washington County, UT R+51
- Vanderburgh County, IN R+9
- Boone County, MO D+14
- Johnson County, TX R+50
- Imperial County, CA Even
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.