91786 leans slightly Democratic by roughly 8 points: about 54% of voters vote Democratic and 46% Republican.
About 52% of adults in 91786 typically vote, below the U.S. average of about 62%. Among adults in 91786, ~28% vote Democratic, ~24% Republican, and ~48% don't vote. The map below shows estimated turnout by block group.
How 91786 compares
Among zip codes within 15 miles, 91786 leans more Democratic than 17 of 38 neighbors.
91786 runs about 13 points more Republican than California as a whole.
Politics vary noticeably by block within 91786. The southwest side runs the most Democratic (D+17) and the northwest side runs the most Republican (R+5), a spread of about 22 points.
Why 91786 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 91786, not a ranked or complete list of what matters most.
Dense areas vote Democratic. More than 99% of residents in 91786 live in densely developed areas, about 63 points above the U.S. average of 36%. A high never-married share predicts Democratic voting, and about 40% of adults in 91786 have never been married, above 88% of zip codes.
Paved land cover and Democratic lean
Places with extensive paved surfaces tend to lean Democratic; 91786, 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 91786 looks the way it does
Renters vote less often than owners. About 53% of households in 91786 rent, about 28 points above the U.S. average of 25%. Limited routine healthcare access lines up with lower turnout, and 91786 sits in the bottom quarter on routine-care measures. Crowded housing lines up with lower turnout, and about 9% of homes in 91786 have more than one occupant per room, above 95% 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.