91203 leans Democratic by roughly 18 points: about 59% of voters vote Democratic and 41% Republican.
About 48% of adults in 91203 typically vote, below the U.S. average of about 62%. Among adults in 91203, ~28% vote Democratic, ~20% Republican, and ~52% don't vote. The map below shows estimated turnout by block group.
How 91203 compares
Among zip codes within 15 miles, 91203 leans more Democratic than 21 of 143 neighbors.
Politically, 91203 sits close to the rest of California.
Politics vary noticeably by block within 91203. The southeast side is the most Democratic-leaning (D+31) and the west side is the least Democratic-leaning (D+2), a spread of about 29 points.
Why 91203 leans the way it does
This analysis examined 14,881 data points per zip code to find what predicts political lean and turnout. The items below are a few correlations that stood out for 91203, not a ranked or complete list of what matters most.
Dense areas vote Democratic. More than 99% of residents in 91203 live in densely developed areas, about 64 points above the U.S. average of 36%. High college attainment predicts Democratic voting, and 91203 sits in the top quarter (about 48%, above 88% of zip codes). A high never-married share predicts Democratic voting, and about 41% of adults in 91203 have never been married, above 89% of zip codes.
Paved land cover and Democratic lean
Places with extensive paved surfaces tend to lean Democratic; 91203, 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 91203 looks the way it does
Renters vote less often than owners. About 81% of households in 91203 rent, about 56 points above the U.S. average of 25%. Crowded housing lines up with lower turnout, and about 8% of homes in 91203 have more than one occupant per room, above 93% of zip codes. Learn more about the findings and methodology on the political spectrum map.
Nearby Zip Codes
Zip Codes with Similar Populations
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.