Polk County leans slightly Democratic by roughly 12 points: about 56% of voters vote Democratic and 44% Republican.
About 76% of adults in Polk County typically vote, above the U.S. average of about 62%. Among adults in Polk County, ~42% vote Democratic, ~33% Republican, and ~25% don't vote. The map below shows estimated turnout by block group.
How Polk County compares
Among counties within 50 miles, Polk County leans more Democratic than 12 of 13 neighbors.
Polk County runs about 25 points more Democratic than Iowa as a whole. Iowa leans Republican overall, while Polk County is one of the few Democratic-leaning pockets.
Politics vary noticeably by city within Polk County. The south side runs the most Democratic (D+29) and the northeast side runs the most Republican (R+8), a spread of about 36 points.
Why Polk 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 Polk County, not a ranked or complete list of what matters most.
Dense areas vote Democratic. About 80% of residents in Polk County live in densely developed areas, about 44 points above the U.S. average of 36%. High college attainment predicts Democratic voting, and Polk County sits in the top quarter (about 40%, above 91% of counties). Polk 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; Polk County, IA sits in the top tenth nationally on this measure.
Why turnout in Polk County looks the way it does
Areas with strong routine healthcare access turn out at higher rates. Polk 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 67%, about 7 points above the U.S. average of 60%. Learn more about the findings and methodology on the political spectrum map.
Nearby Counties
- Dallas County, IA R+7
- Warren County, IA R+24
- Madison County, IA R+41
- Story County, IA D+14
- Jasper County, IA R+28
- Boone County, IA R+24
- Marion County, IA R+34
- Guthrie County, IA R+41
- Clarke County, IA R+41
- Lucas County, IA R+44
Counties with Similar Populations
- Ada County, ID R+8
- Richmond County, NY R+21
- Sonoma County, CA D+42
- Washoe County, NV D+3
- Lake County, IN D+14
- Prince William County, VA D+21
- Clark County, WA D+7
- Knox County, TN R+13
- Onondaga County, NY D+21
- Morris County, NJ Even
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.