91401 leans heavily Democratic by roughly 34 points: about 67% of voters vote Democratic and 33% Republican.
About 49% of adults in 91401 typically vote, below the U.S. average of about 62%. Among adults in 91401, ~33% vote Democratic, ~16% Republican, and ~51% don't vote. The map below shows estimated turnout by block group.
How 91401 compares
Among zip codes within 15 miles, 91401 leans more Democratic than 53 of 125 neighbors.
91401 runs about 13 points more Democratic than California as a whole.
Politics vary noticeably by block within 91401. The southwest side is the most Democratic-leaning (D+53) and the northeast side is the least Democratic-leaning (D+25), a spread of about 28 points.
Why 91401 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 91401, not a ranked or complete list of what matters most.
Dense areas vote Democratic. More than 99% of residents in 91401 live in densely developed areas, about 64 points above the U.S. average of 36%. High college attainment predicts Democratic voting, and 91401 sits in the top quarter (about 38%, above 78% of zip codes). A high never-married share predicts Democratic voting, and about 43% of adults in 91401 have never been married, above 90% of zip codes.
Population density and Democratic lean
Places with high population density tend to lean Democratic; 91401, CA sits in the top tenth nationally on this measure.
Why turnout in 91401 looks the way it does
Renters vote less often than owners. About 68% of households in 91401 rent, about 43 points above the U.S. average of 25%. Limited routine healthcare access lines up with lower turnout, and 91401 sits in the bottom quarter on routine-care measures. High food insecurity lines up with lower turnout, and about 22% of adults in 91401 report food insecurity, 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.