South San Francisco, CA Political Map | Democrat & Republican Areas in South San Francisco

By the BestNeighborhood data science team. Last updated May 2026.

South San Francisco leans heavily Democratic by roughly 42 points: about 71% of voters vote Democratic and 29% Republican.

 

About 54% of adults in South San Francisco typically vote, below the U.S. average of about 62%. Among adults in South San Francisco, ~38% vote Democratic, ~16% Republican, and ~46% don't vote. The map below shows estimated turnout by block group.

How South San Francisco compares

Among cities within 25 miles, South San Francisco leans more Democratic than 22 of 75 neighbors.

South San Francisco runs about 22 points more Democratic than California as a whole.

Politics vary noticeably by neighborhood within South San Francisco. The east side is the most Democratic-leaning (D+47) and the southeast side is the least Democratic-leaning (D+34), a spread of about 12 points.

Why South San Francisco 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 South San Francisco, not a ranked or complete list of what matters most.

Dense areas vote Democratic. About 96% of residents in South San Francisco live in densely developed areas, about 60 points above the U.S. average of 36%. High college attainment predicts Democratic voting, and South San Francisco sits in the top quarter (about 40%, above 87% of cities). A high never-married share predicts Democratic voting, and about 35% of adults in South San Francisco have never been married, above 88% of cities.

Paved land cover and Democratic lean

Places with extensive paved surfaces tend to lean Democratic; South San Francisco, CA sits in the top tenth nationally on this measure. Paved ground does not change how people vote; it mostly reflects how urban and built-up a place is.

Why turnout in South San Francisco looks the way it does

Renters vote less often than owners. About 41% of households in South San Francisco rent, about 16 points above the U.S. average of 25%. Crowded housing lines up with lower turnout, and about 9% of homes in South San Francisco have more than one occupant per room, above 96% of cities. Low high-school completion lines up with lower turnout, and about 86% of adults in South San Francisco have completed high school, below 77% of cities. Learn more about the findings and methodology on the political spectrum map.

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.