90503 leans Democratic by roughly 22 points: about 61% of voters vote Democratic and 39% Republican.
About 64% of adults in 90503 typically vote, near the U.S. average of about 62%. Among adults in 90503, ~39% vote Democratic, ~25% Republican, and ~36% don't vote. The map below shows estimated turnout by block group.
How 90503 compares
Among zip codes within 15 miles, 90503 leans more Democratic than 10 of 92 neighbors.
Politically, 90503 sits close to the rest of California.
Politics vary noticeably by block within 90503. The west side is the most Democratic-leaning (D+27) and the east side is the least Democratic-leaning (D+16), a spread of about 11 points.
Why 90503 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 90503, not a ranked or complete list of what matters most.
Dense areas vote Democratic. More than 99% of residents in 90503 live in densely developed areas, about 63 points above the U.S. average of 36%. High college attainment predicts Democratic voting, and 90503 sits in the top quarter (about 56%, above 92% of zip codes).
Preventive-care access and voter turnout
Places with strong routine preventive-care access tend to turn out at a higher rate; 90503, CA sits in the top quarter nationally on this measure. Dental visits do not drive turnout; the rate reflects income, insurance, and healthcare access, which line up with who votes.
Why turnout in 90503 looks the way it does
Areas with strong routine healthcare access turn out at higher rates. 90503 is in the top quarter nationally for routine-care measures such as insurance coverage, preventive screenings, and dental visits. The dental-visit rate here is about 71%, about 11 points above the U.S. average of 60%. High high-school completion lines up with higher turnout, and about 96% of adults in 90503 have completed high school, above 83% 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.