Marion County leans Democratic by roughly 30 points: about 65% of voters vote Democratic and 35% Republican.
About 59% of adults in Marion County typically vote, near the U.S. average of about 62%. Among adults in Marion County, ~38% vote Democratic, ~21% Republican, and ~41% don't vote. The map below shows estimated turnout by block group.
How Marion County compares
Among counties within 50 miles, Marion County is the most Democratic-leaning.
Marion County runs about 48 points more Democratic than Indiana as a whole. Indiana leans Republican overall, while Marion County is one of the few Democratic-leaning pockets.
Politics vary noticeably by city within Marion County. The northwest side runs the most Democratic (D+56) and the southeast side runs the most Republican (R+9), a spread of about 65 points.
Why Marion 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 Marion County, not a ranked or complete list of what matters most.
Dense areas vote Democratic. About 92% of residents in Marion County live in densely developed areas, about 56 points above the U.S. average of 36%. High college attainment predicts Democratic voting, and Marion County sits in the top quarter (about 34%, above 84% of counties). Marion County runs against the grain of Indiana, a Democratic-leaning pocket in a Republican-leaning state.
Walkability and Democratic lean
Places with a highly walkable street grid tend to lean Democratic; Marion County, IN sits in the top tenth nationally on this measure. A walkable street grid does not change how people vote; it mostly reflects how urban a place is.
Why turnout in Marion County looks the way it does
Renters vote less often than owners. About 41% of households in Marion County rent, about 16 points above the U.S. average of 25%. Learn more about the findings and methodology on the political spectrum map.
Nearby Counties
- Hendricks County, IN R+20
- Hamilton County, IN R+5
- Johnson County, IN R+35
- Hancock County, IN R+36
- Boone County, IN R+19
- Morgan County, IN R+51
- Shelby County, IN R+47
- Madison County, IN R+25
- Tipton County, IN R+52
- Rush County, IN R+57
Counties with Similar Populations
- Prince George's County, MD D+71
- Pinellas County, FL R+3
- Duval County, FL D+7
- Gwinnett County, GA D+21
- Bergen County, NJ D+5
- Erie County, NY D+15
- St. Louis County, MO D+28
- Westchester County, NY D+27
- Fresno County, CA D+3
- Milwaukee County, WI D+41
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.