San Francisco County is a Democratic stronghold. About 80% of voters here vote Democratic and 20% Republican.
About 60% of adults in San Francisco County typically vote, near the U.S. average of about 62%. Among adults in San Francisco County, ~48% vote Democratic, ~12% Republican, and ~40% don't vote. The map below shows estimated turnout by block group.
How San Francisco County compares
Among counties within 50 miles, San Francisco County is the most Democratic-leaning.
San Francisco County runs about 41 points more Democratic than California as a whole.
Politics vary noticeably by city within San Francisco County. The east side is the most Democratic-leaning (D+72) and the southeast side is the least Democratic-leaning (D+48), a spread of about 25 points.
Why San Francisco 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 San Francisco County, not a ranked or complete list of what matters most.
Dense areas vote Democratic. About 98% of residents in San Francisco County live in densely developed areas, about 62 points above the U.S. average of 36%. High college attainment predicts Democratic voting, and San Francisco County sits in the top quarter (about 60%, in the top fraction of counties). A high never-married share predicts Democratic voting, and about 45% of adults in San Francisco County have never been married, above 97% of counties.
Population density and Democratic lean
Places with high population density tend to lean Democratic; San Francisco County, CA sits in the top tenth nationally on this measure.
Why turnout in San Francisco County looks the way it does
Renters vote less often than owners. About 59% of households in San Francisco County rent, about 34 points above the U.S. average of 25%. Crowded housing lines up with lower turnout, and about 7% of homes in San Francisco County have more than one occupant per room, above 96% of counties. Learn more about the findings and methodology on the political spectrum map.
Nearby Counties
- San Mateo County, CA D+48
- Marin County, CA D+48
- Alameda County, CA D+49
- Contra Costa County, CA D+36
- Solano County, CA D+21
- Napa County, CA D+32
- Santa Clara County, CA D+32
- Sonoma County, CA D+42
- Santa Cruz County, CA D+49
- San Joaquin County, CA D+4
Counties with Similar Populations
- Hidalgo County, TX R+2
- Macomb County, MI R+10
- El Paso County, TX D+15
- Essex County, NJ D+48
- Middlesex County, NJ D+11
- Worcester County, MA D+12
- Montgomery County, PA D+21
- Baltimore County, MD D+28
- Ventura County, CA D+16
- Denton County, TX R+7
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.