Summit County leans Democratic by roughly 24 points: about 62% of voters vote Democratic and 38% Republican.
About 93% of adults in Summit County typically vote, above the U.S. average of about 62%. Among adults in Summit County, ~58% vote Democratic, ~35% Republican, and ~7% don't vote. The map below shows estimated turnout by block group.
How Summit County compares
Among counties within 50 miles, Summit County leans more Democratic than 5 of 6 neighbors.
Summit County runs about 12 points more Democratic than Colorado as a whole.
Why Summit 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 Summit County, not a ranked or complete list of what matters most.
Areas with high college attainment vote Democratic. About 55% of adults in Summit County hold a bachelor's degree, about 27 points above the U.S. average of 28%. A high never-married share predicts Democratic voting, and about 40% of adults in Summit County have never been married, above 93% of counties.
Preventive-care access and voter turnout
Places with strong routine preventive-care access tend to turn out at a higher rate; Summit County, CO sits in the top quarter nationally on this measure. Dental visits do not drive turnout; the rate reflects income, insurance, and healthcare access, which line up with who votes.
Why turnout in Summit County looks the way it does
Areas with strong routine healthcare access turn out at higher rates. Summit 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%. High high-school completion lines up with higher turnout, and about 96% of adults in Summit County have completed high school, above 95% of counties. Learn more about the findings and methodology on the political spectrum map.
Nearby Counties
- Lake County, CO D+25
- Park County, CO R+9
- Clear Creek County, CO D+21
- Grand County, CO R+6
- Eagle County, CO D+14
- Gilpin County, CO D+16
- Jefferson County, CO D+18
- Pitkin County, CO D+40
- Boulder County, CO D+52
- Broomfield County, CO D+25
Counties with Similar Populations
- Bee County, TX R+22
- Kleberg County, TX R+6
- Stone County, MO R+55
- Williamsburg County, SC D+26
- Washington County, ME R+24
- Elk County, PA R+42
- Bolivar County, MS D+34
- Lake County, MT R+21
- Wabash County, IN R+48
- Clarendon County, SC R+8
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Sources and methodology
Precinct-level voting records used to fit the model come from Colorado 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.