Marshall County leans Republican by roughly 18 points: about 41% of voters vote Democratic and 59% Republican.
About 74% of adults in Marshall County typically vote, above the U.S. average of about 62%. Among adults in Marshall County, ~30% vote Democratic, ~44% Republican, and ~26% don't vote. The map below shows estimated turnout by block group.
How Marshall County compares
Among counties within 50 miles, Marshall County leans more Republican than 3 of 13 neighbors.
Marshall County runs about 4 points more Republican than Iowa as a whole.
Politics vary noticeably by city within Marshall County. The southwest side is the most Republican-leaning (R+44) and the east side is the least Republican-leaning (R+8), a spread of about 37 points.
Why Marshall 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 Marshall County, not a ranked or complete list of what matters most.
Marshall County votes Republican even though it is densely developed (about 50%, far above the Iowa average of 16%). State and regional patterns outweigh the Democratic lean that density usually predicts here.
Walkability and Democratic lean
Places with a highly walkable street grid tend to lean Democratic; Marshall County, IA 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 Marshall County looks the way it does
Turnout in Marshall 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
- Tama County, IA R+25
- Jasper County, IA R+28
- Grundy County, IA R+42
- Poweshiek County, IA R+19
- Hardin County, IA R+40
- Story County, IA D+14
- Black Hawk County, IA D+3
- Polk County, IA D+12
- Marion County, IA R+34
- Butler County, IA R+43
Counties with Similar Populations
- Mower County, MN R+13
- Murray County, GA R+68
- Pike County, MS D+8
- Orleans County, NY R+32
- Rio Arriba County, NM D+20
- Ottawa County, OH R+30
- Delaware County, OK R+58
- Tazewell County, VA R+58
- McKean County, PA R+43
- LaGrange County, IN R+63
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.