Hamilton County leans slightly Republican by roughly 6 points: about 47% of voters vote Democratic and 53% Republican.
About 83% of adults in Hamilton County typically vote, above the U.S. average of about 62%. Among adults in Hamilton County, ~39% vote Democratic, ~44% Republican, and ~17% don't vote. The map below shows estimated turnout by block group.
How Hamilton County compares
Among counties within 50 miles, Hamilton County leans more Republican than 1 of 19 neighbors.
Hamilton County runs about 14 points more Democratic than Indiana as a whole.
Politics vary noticeably by city within Hamilton County. The southwest side runs the most Democratic (D+8) and the northeast side runs the most Republican (R+29), a spread of about 37 points.
Why Hamilton 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 Hamilton County, not a ranked or complete list of what matters most.
Hamilton County votes Republican even though it is densely developed (about 78%, far above the Indiana average of 25%). State and regional patterns outweigh the Democratic lean that density usually predicts here. A high family-household share predicts Republican voting, and about 75% of households in Hamilton County are family households, above 95% of counties.
Food insecurity and voter turnout
Places with low food insecurity tend to turn out at a higher rate; Hamilton County, IN sits in the bottom tenth nationally on this measure. Food insecurity does not directly drive turnout; it reflects economic hardship, which lines up with lower voting.
Why turnout in Hamilton County looks the way it does
Areas with strong routine healthcare access turn out at higher rates. Hamilton County 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 97% of adults in Hamilton County have completed high school, in the top fraction of counties. Learn more about the findings and methodology on the political spectrum map.
Nearby Counties
- Marion County, IN D+29
- Boone County, IN R+19
- Hancock County, IN R+36
- Madison County, IN R+25
- Tipton County, IN R+52
- Hendricks County, IN R+20
- Johnson County, IN R+35
- Clinton County, IN R+45
- Howard County, IN R+30
- Henry County, IN R+47
Counties with Similar Populations
- Marion County, OR D+3
- Somerset County, NJ D+15
- Galveston County, TX R+13
- Horry County, SC R+30
- Nueces County, TX R+4
- Rutherford County, TN R+16
- Westmoreland County, PA R+26
- Rockland County, NY R+14
- Douglas County, CO R+7
- Larimer County, CO D+16
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Sources and methodology
Precinct-level voting records used to fit the model come from Indiana 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.