91737 leans slightly Republican by roughly 12 points: about 44% of voters vote Democratic and 56% Republican.
About 72% of adults in 91737 typically vote, above the U.S. average of about 62%. Among adults in 91737, ~32% vote Democratic, ~40% Republican, and ~28% don't vote. The map below shows estimated turnout by block group.
How 91737 compares
Among zip codes within 15 miles, 91737 leans more Republican than 29 of 31 neighbors.
91737 runs about 32 points more Republican than California as a whole. California leans Democratic overall, while 91737 is one of the few Republican-leaning pockets.
Politics vary noticeably by block within 91737. The north side is the most split-leaning (R+27) and the southeast side is the least split-leaning (Even), a spread of about 25 points.
Why 91737 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 91737, not a ranked or complete list of what matters most.
91737 votes Republican even though it is densely developed (about 93%, far above the California average of 58%). State and regional patterns outweigh the Democratic lean that density usually predicts here. A high family-household share predicts Republican voting, and about 81% of households in 91737 are family households, above 93% of zip codes. 91737 runs against the grain of California, a Republican-leaning pocket in a Democratic-leaning state.
Population density and Democratic lean
Places with high population density tend to lean Democratic; 91737, CA sits in the top quarter nationally on this measure.
Why turnout in 91737 looks the way it does
Turnout in 91737 sits close to the national pattern. Routine healthcare access, homeownership, education, and food security all land near their national averages here. 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.