O'Brien County is a Republican stronghold. About 23% of voters here vote Democratic and 77% Republican.
About 92% of adults in O'Brien County typically vote, above the U.S. average of about 62%. Among adults in O'Brien County, ~21% vote Democratic, ~71% Republican, and ~8% don't vote. The map below shows estimated turnout by block group.
How O'Brien County compares
Among counties within 50 miles, O'Brien County leans more Republican than 8 of 11 neighbors.
O'Brien County runs about 41 points more Republican than Iowa as a whole.
Politics vary noticeably by city within O'Brien County. The southwest side is the most Republican-leaning (R+66) and the northwest side is the least Republican-leaning (R+48), a spread of about 18 points.
Why O'Brien County leans the way it does
Density, race composition, education, and family structure all sit close to their national averages in O'Brien County. The lean here lands roughly where demographic data alone would predict.
Park access and Republican lean
Places with low park coverage tend to lean Republican; O'Brien County, IA sits in the bottom quarter nationally on this measure. Park access does not change how people vote; it tends to track denser, higher-income areas.
Why turnout in O'Brien County looks the way it does
Turnout in O'Brien 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
- Osceola County, IA R+57
- Sioux County, IA R+55
- Cherokee County, IA R+42
- Clay County, IA R+34
- Lyon County, IA R+65
- Dickinson County, IA R+34
- Nobles County, MN R+28
- Plymouth County, IA R+49
- Buena Vista County, IA R+21
- Rock County, MN R+45
Counties with Similar Populations
- Rusk County, WI R+38
- Cedar County, MO R+65
- Gulf County, FL R+56
- Franklin County, ID R+77
- Claiborne Parish, LA R+11
- Massac County, IL R+46
- Estill County, KY R+63
- Choctaw County, OK R+54
- Smith County, MS R+59
- Atoka County, OK R+69
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.