91766 leans Democratic by roughly 28 points: about 64% of voters vote Democratic and 36% Republican.
About 41% of adults in 91766 typically vote, below the U.S. average of about 62%. Among adults in 91766, ~26% vote Democratic, ~15% Republican, and ~59% don't vote. The map below shows estimated turnout by block group.
How 91766 compares
Among zip codes within 15 miles, 91766 leans more Democratic than 46 of 50 neighbors.
91766 runs about 8 points more Democratic than California as a whole.
Politics vary noticeably by block within 91766. The north side is the most Democratic-leaning (D+38) and the southwest side is the least Democratic-leaning (D+22), a spread of about 16 points.
Why 91766 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 91766, not a ranked or complete list of what matters most.
Dense areas vote Democratic. About 97% of residents in 91766 live in densely developed areas, about 61 points above the U.S. average of 36%. A high never-married share predicts Democratic voting, and about 43% of adults in 91766 have never been married, above 91% of zip codes.
Paved land cover and Democratic lean
Places with extensive paved surfaces tend to lean Democratic; 91766, 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 91766 looks the way it does
Areas with limited routine healthcare access turn out at lower rates. 91766 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 45% of households in 91766 rent, about 20 points above the U.S. average of 25%. High food insecurity lines up with lower turnout, and about 29% of adults in 91766 report food insecurity, above 93% 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.