San Diego County, CA Political Map | Democrat & Republican Areas in San Diego County

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

San Diego County leans Democratic by roughly 18 points: about 59% of voters vote Democratic and 41% Republican.

 

About 62% of adults in San Diego County typically vote, near the U.S. average of about 62%. Among adults in San Diego County, ~37% vote Democratic, ~25% Republican, and ~38% don't vote. The map below shows estimated turnout by block group.

How San Diego County compares

Politically, San Diego County sits close to the rest of California.

Politics vary noticeably by city within San Diego County. The south side runs the most Democratic (D+33) and the northeast side runs the most Republican (R+9), a spread of about 43 points.

Why San Diego 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 Diego County, not a ranked or complete list of what matters most.

Dense areas vote Democratic. About 87% of residents in San Diego County live in densely developed areas, about 51 points above the U.S. average of 36%. High college attainment predicts Democratic voting, and San Diego County sits in the top quarter (about 42%, above 93% of counties). A high never-married share predicts Democratic voting, and about 36% of adults in San Diego County have never been married, above 87% of counties.

Walkability and Democratic lean

Places with a highly walkable street grid tend to lean Democratic; San Diego County, CA 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 San Diego County looks the way it does

Renters vote less often than owners. About 44% of households in San Diego County rent, about 19 points above the U.S. average of 25%. Crowded housing lines up with lower turnout, and about 7% of homes in San Diego County have more than one occupant per room, above 96% of counties. 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.