Decatur County leans heavily Republican by roughly 44 points: about 28% of voters vote Democratic and 72% Republican.
About 79% of adults in Decatur County typically vote, above the U.S. average of about 62%. Among adults in Decatur County, ~22% vote Democratic, ~57% Republican, and ~21% don't vote. The map below shows estimated turnout by block group.
How Decatur County compares
Among counties within 50 miles, Decatur County leans more Republican than 6 of 15 neighbors.
Decatur County runs about 31 points more Republican than Iowa as a whole.
Politics vary noticeably by city within Decatur County. The northeast side is the most Republican-leaning (R+61) and the southwest side is the least Republican-leaning (R+25), a spread of about 36 points.
Why Decatur 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 Decatur County, not a ranked or complete list of what matters most.
Rural areas with a high white share vote Republican. Decatur County sits in the bottom quarter on density and about 91% of residents are non-Hispanic white, about 18 points above the U.S. average of 72%.
Paved land cover and Republican lean
Places with little paved surface tend to lean Republican; Decatur County, IA sits below the national average on this measure. Paved ground does not change how people vote; it mostly reflects how urban and built-up a place is.
Why turnout in Decatur County looks the way it does
Turnout in Decatur 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
- Ringgold County, IA R+50
- Clarke County, IA R+41
- Mercer County, MO R+70
- Wayne County, IA R+56
- Harrison County, MO R+64
- Lucas County, IA R+44
- Union County, IA R+33
- Worth County, MO R+64
- Grundy County, MO R+57
- Madison County, IA R+41
Counties with Similar Populations
- Benton County, MS R+26
- Pleasants County, WV R+59
- McCulloch County, TX R+56
- Kane County, UT R+59
- Merrick County, NE R+60
- Red River Parish, LA R+19
- Franklin County, MS R+35
- Boise County, ID R+50
- Coleman County, TX R+63
- Washakie County, WY R+64
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.