91501 leans Democratic by roughly 16 points: about 58% of voters vote Democratic and 42% Republican.
About 61% of adults in 91501 typically vote, near the U.S. average of about 62%. Among adults in 91501, ~35% vote Democratic, ~26% Republican, and ~39% don't vote. The map below shows estimated turnout by block group.
How 91501 compares
Among zip codes within 15 miles, 91501 leans more Democratic than 11 of 131 neighbors.
91501 runs about 5 points more Republican than California as a whole.
Politics vary noticeably by block within 91501. The southwest side is the most Democratic-leaning (D+31) and the northeast side is the least Democratic-leaning (D+3), a spread of about 28 points.
Why 91501 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 91501, not a ranked or complete list of what matters most.
Dense areas vote Democratic. About 94% of residents in 91501 live in densely developed areas, about 58 points above the U.S. average of 36%. High college attainment predicts Democratic voting, and 91501 sits in the top quarter (about 46%, above 86% of zip codes). A high never-married share predicts Democratic voting, and about 38% of adults in 91501 have never been married, above 84% of zip codes.
Paved land cover and Democratic lean
Places with extensive paved surfaces tend to lean Democratic; 91501, 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 91501 looks the way it does
Renters vote less often than owners. About 56% of households in 91501 rent, about 32 points above the U.S. average of 25%. Crowded housing lines up with lower turnout, and about 7% of homes in 91501 have more than one occupant per room, above 92% 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.