Sumter County leans slightly Democratic by roughly 8 points: about 54% of voters vote Democratic and 46% Republican.
About 69% of adults in Sumter County typically vote, above the U.S. average of about 62%. Among adults in Sumter County, ~37% vote Democratic, ~32% Republican, and ~31% don't vote. The map below shows estimated turnout by block group.
How Sumter County compares
Among counties within 50 miles, Sumter County leans more Democratic than 6 of 11 neighbors.
Sumter County runs about 27 points more Democratic than South Carolina as a whole. South Carolina leans Republican overall, while Sumter County is one of the few Democratic-leaning pockets.
Politics vary noticeably by city within Sumter County. The east side runs the most Democratic (D+53) and the southwest side runs the most Republican (R+17), a spread of about 71 points.
Why Sumter 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 Sumter County, not a ranked or complete list of what matters most.
Density combined with diversity predicts Democratic voting. Non-Hispanic white share in Sumter County is about 44%, about 29 points below the U.S. average of 72%. A high never-married share predicts Democratic voting, and about 34% of adults in Sumter County have never been married, above 82% of counties. Sumter County runs against the grain of South Carolina, a Democratic-leaning pocket in a Republican-leaning state.
Developed land and Democratic lean
Places with a heavily developed built environment tend to lean Democratic; Sumter County, SC sits in the top quarter nationally on this measure. Developed land does not change how people vote; it mostly reflects how urban a place is.
Why turnout in Sumter County looks the way it does
Areas with strong routine healthcare access turn out at higher rates. Sumter 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 56%, below 66% of counties. Learn more about the findings and methodology on the political spectrum map.
Nearby Counties
- Lee County, SC D+20
- Clarendon County, SC R+8
- Kershaw County, SC R+32
- Calhoun County, SC R+15
- Richland County, SC D+38
- Darlington County, SC R+8
- Florence County, SC Even
- Orangeburg County, SC D+28
- Williamsburg County, SC D+26
- Lexington County, SC R+30
Counties with Similar Populations
- Eau Claire County, WI D+10
- Tompkins County, NY D+49
- Monongalia County, WV D+4
- Woodbury County, IA R+9
- Vigo County, IN R+12
- Franklin County, MO R+48
- Walworth County, WI R+17
- Navajo County, AZ R+3
- Platte County, MO R+5
- Flathead County, MT R+32
Sources and methodology
Precinct-level voting records used to fit the model come from South Carolina State Election Commission, 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.