San Bruno leans heavily Democratic by roughly 44 points: about 72% of voters vote Democratic and 28% Republican.
About 61% of adults in San Bruno typically vote, near the U.S. average of about 62%. Among adults in San Bruno, ~44% vote Democratic, ~17% Republican, and ~39% don't vote. The map below shows estimated turnout by block group.
How San Bruno compares
Among cities within 25 miles, San Bruno leans more Democratic than 24 of 75 neighbors.
San Bruno runs about 23 points more Democratic than California as a whole.
Politics vary noticeably by neighborhood within San Bruno. The northwest side is the most Democratic-leaning (D+47) and the northeast side is the least Democratic-leaning (D+37), a spread of about 10 points.
Why San Bruno 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 San Bruno, not a ranked or complete list of what matters most.
Dense areas vote Democratic. About 97% of residents in San Bruno live in densely developed areas, about 61 points above the U.S. average of 36%. High college attainment predicts Democratic voting, and San Bruno sits in the top quarter (about 44%, above 90% of cities). A high never-married share predicts Democratic voting, and about 37% of adults in San Bruno have never been married, above 90% of cities.
Population density and Democratic lean
Places with high population density tend to lean Democratic; San Bruno, CA sits in the top tenth nationally on this measure.
Why turnout in San Bruno looks the way it does
Renters vote less often than owners. About 37% of households in San Bruno rent, about 12 points above the U.S. average of 25%. Crowded housing lines up with lower turnout, and about 7% of homes in San Bruno have more than one occupant per room, above 94% of cities. Learn more about the findings and methodology on the political spectrum map.
Nearby Cities
- South San Francisco, CA D+43
- Millbrae, CA D+40
- Millbrae Meadows, CA D+33
- Pacifica, CA D+43
- Colma, CA D+39
- Pedro Valley, CA D+32
- Brisbane, CA D+50
- Burlingame, CA D+52
- Daly City, CA D+39
- Hillsborough, CA D+41
Cities with Similar Populations
- West Bend, WI R+23
- Chatsworth, CA D+16
- North Atlanta, GA D+38
- Sun Prairie, WI D+37
- Leominster, MA D+9
- Bear, DE D+32
- Moline, IL D+16
- Morrisville, NC D+37
- Golden, CO D+29
- Bullhead City, AZ R+30
Sources and methodology
Precinct-level voting records used to fit the model come from California 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.