Santa Clara County leans heavily Democratic by roughly 32 points: about 66% of voters vote Democratic and 34% Republican.
About 56% of adults in Santa Clara County typically vote, below the U.S. average of about 62%. Among adults in Santa Clara County, ~37% vote Democratic, ~19% Republican, and ~44% don't vote. The map below shows estimated turnout by block group.
How Santa Clara County compares
Among counties within 50 miles, Santa Clara County leans more Democratic than 1 of 6 neighbors.
Santa Clara County runs about 12 points more Democratic than California as a whole.
Politics vary noticeably by city within Santa Clara County. The northwest side is the most Democratic-leaning (D+44) and the southeast side is the least Democratic-leaning (D+21), a spread of about 22 points.
Why Santa Clara County leans the way it does
This analysis examined 14,881 data points per county to find what predicts political lean and turnout. The items below are a few correlations that stood out for Santa Clara County, not a ranked or complete list of what matters most.
Dense areas vote Democratic. About 96% of residents in Santa Clara County live in densely developed areas, about 59 points above the U.S. average of 36%. High college attainment predicts Democratic voting, and Santa Clara County sits in the top quarter (about 56%, above 98% of counties). A high never-married share predicts Democratic voting, and about 35% of adults in Santa Clara County have never been married, above 85% of counties.
Population density and Democratic lean
Places with high population density tend to lean Democratic; Santa Clara County, CA sits in the top tenth nationally on this measure.
Why turnout in Santa Clara County looks the way it does
Renters vote less often than owners. About 43% of households in Santa Clara County rent, about 18 points above the U.S. average of 25%. Strong routine healthcare access lines up with higher turnout, and Santa Clara County sits in the top quarter on routine-care measures. Crowded housing lines up with lower turnout, and about 8% of homes in Santa Clara County have more than one occupant per room, above 97% of counties. Learn more about the findings and methodology on the political spectrum map.
Nearby Counties
- Santa Cruz County, CA D+49
- Alameda County, CA D+49
- San Mateo County, CA D+48
- San Francisco County, CA D+61
- San Benito County, CA D+12
- Contra Costa County, CA D+36
- Monterey County, CA D+29
- San Joaquin County, CA D+4
- Stanislaus County, CA R+8
- Marin County, CA D+48
Counties with Similar Populations
- Broward County, FL D+20
- Bexar County, TX D+14
- Wayne County, MI D+33
- Tarrant County, TX D+3
- New York County, NY D+62
- San Bernardino County, CA Even
- Alameda County, CA D+49
- Middlesex County, MA D+37
- Clark County, NV D+12
- Philadelphia County, PA D+56
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.