91377 leans Democratic by roughly 24 points: about 62% of voters vote Democratic and 38% Republican.
About 78% of adults in 91377 typically vote, above the U.S. average of about 62%. Among adults in 91377, ~48% vote Democratic, ~30% Republican, and ~22% don't vote. The map below shows estimated turnout by block group.
How 91377 compares
Among zip codes within 15 miles, 91377 leans more Democratic than 22 of 29 neighbors.
Politically, 91377 sits close to the rest of California.
Politics vary noticeably by block within 91377. The south side is the most Democratic-leaning (D+29) and the northeast side is the least Democratic-leaning (D+16), a spread of about 12 points.
Why 91377 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 91377, not a ranked or complete list of what matters most.
Areas with high college attainment vote Democratic. About 63% of adults in 91377 hold a bachelor's degree, about 35 points above the U.S. average of 28%. Density combined with diversity predicts Democratic voting, and non-Hispanic white share in 91377 is about 69%, below 69% of zip codes.
Paved land cover and Democratic lean
Places with extensive paved surfaces tend to lean Democratic; 91377, CA sits in the top quarter 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 91377 looks the way it does
Areas with strong routine healthcare access turn out at higher rates. 91377 is in the top quarter nationally for routine-care measures such as insurance coverage, preventive screenings, and dental visits. The dental-visit rate here is about 74%, about 14 points above the U.S. average of 60%. High high-school completion lines up with higher turnout, and about 99% of adults in 91377 have completed high school, above 96% 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.