St. Clair County leans heavily Republican by roughly 30 points: about 35% of voters vote Democratic and 65% Republican.
About 87% of adults in St. Clair County typically vote, above the U.S. average of about 62%. Among adults in St. Clair County, ~30% vote Democratic, ~57% Republican, and ~13% don't vote. The map below shows estimated turnout by block group.
How St. Clair County compares
Among counties within 50 miles, St. Clair County leans more Republican than 2 of 4 neighbors.
St. Clair County runs about 29 points more Republican than Michigan as a whole.
Politics vary noticeably by city within St. Clair County. The west side is the most Republican-leaning (R+51) and the east side is the least Republican-leaning (R+12), a spread of about 39 points.
Why St. Clair 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 St. Clair County, not a ranked or complete list of what matters most.
St. Clair County votes Republican even though it is densely developed (about 47%, well above the Michigan average of 31%). State and regional patterns outweigh the Democratic lean that density usually predicts here.
Cancer-screening access and voter turnout
Places with high colon-cancer-screening access tend to turn out at a higher rate; St. Clair County, MI sits in the top quarter nationally on this measure. Cancer screening does not drive turnout; it reflects income, insurance, and healthcare access.
Why turnout in St. Clair County looks the way it does
Areas with strong routine healthcare access turn out at higher rates. St. Clair 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 67%, about 7 points above the U.S. average of 60%. Homeowners vote more often than renters, and about 82% of households in St. Clair County own their home, above 87% of counties. Learn more about the findings and methodology on the political spectrum map.
Nearby Counties
- Macomb County, MI R+10
- Sanilac County, MI R+46
- Lapeer County, MI R+38
- Oakland County, MI D+14
- Wayne County, MI D+33
- Tuscola County, MI R+42
- Genesee County, MI D+8
- Huron County, MI R+42
- Livingston County, MI R+23
- Washtenaw County, MI D+44
Counties with Similar Populations
- Ouachita Parish, LA R+13
- Jackson County, MI R+14
- Catawba County, NC R+33
- Indian River County, FL R+21
- Rensselaer County, NY D+6
- Alexandria City, VA D+55
- Comal County, TX R+36
- Dorchester County, SC R+12
- Johnson County, IN R+35
- Portage County, OH R+12
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Sources and methodology
Precinct-level voting records used to fit the model come from Michigan Department 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.