Johnson County leans heavily Democratic by roughly 36 points: about 68% of voters vote Democratic and 32% Republican.
About 75% of adults in Johnson County typically vote, above the U.S. average of about 62%. Among adults in Johnson County, ~51% vote Democratic, ~24% Republican, and ~25% don't vote. The map below shows estimated turnout by block group.
How Johnson County compares
Among counties within 50 miles, Johnson County is the most Democratic-leaning.
Johnson County runs about 49 points more Democratic than Iowa as a whole. Iowa leans Republican overall, while Johnson County is one of the few Democratic-leaning pockets.
Politics vary noticeably by city within Johnson County. The east side runs the most Democratic (D+52) and the southwest side runs the most Republican (R+4), a spread of about 57 points.
Why Johnson 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 Johnson County, not a ranked or complete list of what matters most.
Areas with high college attainment vote Democratic. About 56% of adults in Johnson County hold a bachelor's degree, about 27 points above the U.S. average of 28%. Dense areas vote Democratic, and Johnson County sits in the top fifth on density (about 66%, above 89% of counties). Johnson County runs against the grain of Iowa, a Democratic-leaning pocket in a Republican-leaning state.
Population density and Democratic lean
Places with high population density tend to lean Democratic; Johnson County, IA sits in the top tenth nationally on this measure.
Why turnout in Johnson County looks the way it does
Areas with strong routine healthcare access turn out at higher rates. Johnson 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 68%, about 8 points above the U.S. average of 60%. High high-school completion lines up with higher turnout, and about 96% of adults in Johnson County have completed high school, above 96% of counties. Learn more about the findings and methodology on the political spectrum map.
Nearby Counties
- Cedar County, IA R+34
- Linn County, IA D+7
- Washington County, IA R+33
- Iowa County, IA R+38
- Muscatine County, IA R+16
- Benton County, IA R+36
- Louisa County, IA R+37
- Jones County, IA R+27
- Keokuk County, IA R+47
- Henry County, IA R+31
Counties with Similar Populations
- Kings County, CA R+10
- Penobscot County, ME R+7
- Merrimack County, NH D+6
- Citrus County, FL R+43
- Cumberland County, NJ D+7
- Berrien County, MI Even
- Canadian County, OK R+37
- Washington County, MD R+18
- Scott County, MN R+5
- Monroe County, MI R+27
Sources and methodology
Precinct-level voting records used to fit the model come from Iowa 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.