96021 leans heavily Republican by roughly 32 points: about 34% of voters vote Democratic and 66% Republican.
About 57% of adults in 96021 typically vote, near the U.S. average of about 62%. Among adults in 96021, ~19% vote Democratic, ~38% Republican, and ~43% don't vote. The map below shows estimated turnout by block group.
How 96021 compares
Among zip codes within 15 miles, 96021 is the least Republican-leaning.
96021 runs about 53 points more Republican than California as a whole. California leans Democratic overall, while 96021 is one of the few Republican-leaning pockets.
Politics vary noticeably by block within 96021. The northeast side is the most Republican-leaning (R+45) and the north side is the least Republican-leaning (R+24), a spread of about 22 points.
Why 96021 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 96021, not a ranked or complete list of what matters most.
96021 votes against the grain of California. California leans Democratic overall, while 96021 runs about 53 points more Republican. Low college attainment predicts Republican voting, and 96021 sits in the bottom quarter (about 15%, below 82% of zip codes).
Cancer-screening access and voter turnout
Places with low colon-cancer-screening access tend to turn out at a lower rate; 96021, CA sits in the bottom tenth nationally on this measure. Cancer screening does not drive turnout; it reflects income, insurance, and healthcare access.
Why turnout in 96021 looks the way it does
Areas with limited routine healthcare access turn out at lower rates. 96021 is in the bottom quarter nationally for routine-care measures such as insurance coverage, preventive screenings, and dental visits. High food insecurity lines up with lower turnout, and about 23% of adults in 96021 report food insecurity, above 85% of zip codes. Low high-school completion lines up with lower turnout, and about 82% of adults in 96021 have completed high school, below 88% 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.