Dewey County leans Democratic by roughly 30 points: about 65% of voters vote Democratic and 35% Republican.
About 59% of adults in Dewey County typically vote, near the U.S. average of about 62%. Among adults in Dewey County, ~38% vote Democratic, ~21% Republican, and ~41% don't vote. The map below shows estimated turnout by block group.
How Dewey County compares
Among counties within 50 miles, Dewey County leans more Democratic than 2 of 3 neighbors.
Dewey County runs about 59 points more Democratic than South Dakota as a whole. South Dakota leans Republican overall, while Dewey County is one of the few Democratic-leaning pockets.
Politics vary noticeably by city within Dewey County. The south side runs the most Democratic (D+60) and the northwest side runs the most Republican (R+51), a spread of about 111 points.
Why Dewey 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 Dewey County, not a ranked or complete list of what matters most.
Dewey County votes against the grain of South Dakota. South Dakota leans Republican overall, while Dewey County runs about 59 points more Democratic. A high never-married share predicts Democratic voting, and about 45% of adults in Dewey County have never been married, above 97% of counties.
Homeownership and voter turnout
Places with renter-heavy households tend to turn out at a lower rate; Dewey County, SD sits in the bottom tenth nationally on this measure.
Why turnout in Dewey County looks the way it does
Areas with limited routine healthcare access turn out at lower rates. Dewey County is in the bottom quarter nationally for routine-care measures such as insurance coverage, preventive screenings, and dental visits. The dental-visit rate here is about 49%, about 17 points below the South Dakota average of 66%. Renters vote less often than owners, and about 40% of households in Dewey County rent, above 93% of counties. High-crime urban areas turn out at lower rates, and Dewey County sits in the top 15% on a violent-crime measure. Learn more about the findings and methodology on the political spectrum map.
Nearby Counties
- Ziebach County, SD D+12
- Corson County, SD D+38
- Walworth County, SD R+56
- Sully County, SD R+62
- Potter County, SD R+62
- Stanley County, SD R+49
- Hughes County, SD R+34
- Campbell County, SD R+66
- Haakon County, SD R+71
- Perkins County, SD R+68
Counties with Similar Populations
- Alexander County, IL R+4
- Martin County, TX R+68
- Aleutians West Census Area, AK Even
- Brule County, SD R+52
- Delta County, TX R+68
- Stevens County, KS R+73
- Warren County, GA D+15
- Polk County, NE R+62
- Coal County, OK R+68
- Carter County, MO R+71
Sources and methodology
Precinct-level voting records used to fit the model come from South Dakota 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.