Boulder is a Democratic stronghold. About 85% of voters here vote Democratic and 15% Republican.
About 78% of adults in Boulder typically vote, above the U.S. average of about 62%. Among adults in Boulder, ~66% vote Democratic, ~12% Republican, and ~22% don't vote. The map below shows estimated turnout by block group.
How Boulder compares
Among cities within 25 miles, Boulder is the most Democratic-leaning.
Boulder runs about 58 points more Democratic than Colorado as a whole.
Politics vary noticeably by neighborhood within Boulder. The north side is the most Democratic-leaning (D+73) and the northeast side is the least Democratic-leaning (D+58), a spread of about 15 points.
Why Boulder leans the way it does
This analysis examined 14,881 data points per city to find what predicts political lean and turnout. The items below are a few correlations that stood out for Boulder, not a ranked or complete list of what matters most.
Areas with high college attainment vote Democratic. About 76% of adults in Boulder hold a bachelor's degree, about 47 points above the U.S. average of 28%. Dense areas vote Democratic, and Boulder sits in the top fifth on density (about 83%, above 95% of cities). A high never-married share predicts Democratic voting, and about 52% of adults in Boulder have never been married, above 98% of cities.
Walkability and Democratic lean
Places with a highly walkable street grid tend to lean Democratic; Boulder, CO 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 Boulder looks the way it does
Areas with strong routine healthcare access turn out at higher rates. Boulder 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 68%, about 8 points above the U.S. average of 60%. High high-school completion lines up with higher turnout, and about 98% of adults in Boulder have completed high school, above 93% of cities. Learn more about the findings and methodology on the political spectrum map.
Nearby Cities
- Gunbarrel, CO D+55
- Eldorado Springs, CO D+53
- Louisville, CO D+59
- Niwot, CO D+47
- Superior, CO D+51
- Jamestown, CO D+61
- Lafayette, CO D+49
- Coal Creek, CO D+21
- Sugarloaf, CO D+68
Cities with Similar Populations
- St. Charles, MO R+6
- Palm Bay, FL R+10
- Bellingham, WA D+49
- Keller, TX R+20
- Newark, DE D+34
- Spring Hill, FL R+28
- Rialto, CA D+20
- Saginaw, MI D+18
- Bethlehem, PA D+16
- Yakima, WA R+4
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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.