91770 leans Democratic by roughly 16 points: about 58% of voters vote Democratic and 42% Republican.
About 38% of adults in 91770 typically vote, below the U.S. average of about 62%. Among adults in 91770, ~22% vote Democratic, ~16% Republican, and ~62% don't vote. The map below shows estimated turnout by block group.
How 91770 compares
Among zip codes within 15 miles, 91770 leans more Democratic than 28 of 132 neighbors.
Politically, 91770 sits close to the rest of California.
Politics vary noticeably by block within 91770. The south side is the most Democratic-leaning (D+26) and the north side is the least Democratic-leaning (D+12), a spread of about 14 points.
Why 91770 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 91770, not a ranked or complete list of what matters most.
Dense areas vote Democratic. More than 99% of residents in 91770 live in densely developed areas, about 64 points above the U.S. average of 36%. A high never-married share predicts Democratic voting, and about 36% of adults in 91770 have never been married, above 81% of zip codes.
Population density and Democratic lean
Places with high population density tend to lean Democratic; 91770, CA sits in the top tenth nationally on this measure.
Why turnout in 91770 looks the way it does
Areas with limited routine healthcare access turn out at lower rates. 91770 is in the bottom quarter nationally for routine-care measures such as insurance coverage, preventive screenings, and dental visits. Renters vote less often than owners, and about 52% of households in 91770 rent, about 27 points above the U.S. average of 25%. High food insecurity lines up with lower turnout, and about 27% of adults in 91770 report food insecurity, above 91% 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.