Hillsborough leans heavily Democratic by roughly 40 points: about 70% of voters vote Democratic and 30% Republican.
About 92% of adults in Hillsborough typically vote, above the U.S. average of about 62%. Among adults in Hillsborough, ~64% vote Democratic, ~27% Republican, and ~9% don't vote. The map below shows estimated turnout by block group.
How Hillsborough compares
Among cities within 25 miles, Hillsborough leans more Democratic than 22 of 70 neighbors.
Hillsborough runs about 20 points more Democratic than California as a whole.
Why Hillsborough leans the way it does
This analysis examined 14,881 data points per city to find what predicts political lean and turnout. The items below are a few correlations that stood out for Hillsborough, not a ranked or complete list of what matters most.
Areas with high college attainment vote Democratic. About 82% of adults in Hillsborough hold a bachelor's degree, about 54 points above the U.S. average of 28%. Dense areas vote Democratic, and Hillsborough sits in the top fifth on density (about 95%, above 98% of cities).
Walkability and Democratic lean
Places with a highly walkable street grid tend to lean Democratic; Hillsborough, CA sits in the top quarter nationally on this measure. A walkable street grid does not change how people vote; it mostly reflects how urban a place is.
Why turnout in Hillsborough looks the way it does
Areas with strong routine healthcare access turn out at higher rates. Hillsborough 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 77%, about 17 points above the U.S. average of 60%. Homeowners vote more often than renters, and about 91% of households in Hillsborough own their home, compared to around 68% in nearby cities. High high-school completion lines up with higher turnout, and about 99% of adults in Hillsborough have completed high school, above 97% of cities. Learn more about the findings and methodology on the political spectrum map.
Nearby Cities
- Burlingame, CA D+52
- Highlands-Baywood Park, CA D+52
- San Mateo, CA D+49
- Millbrae, CA D+40
- Belmont, CA D+53
- Foster City, CA D+50
- San Bruno, CA D+43
- Millbrae Meadows, CA D+33
- San Carlos, CA D+57
- Pedro Valley, CA D+32
Cities with Similar Populations
- Chickamauga, GA R+62
- Laurel, DE R+19
- Walton, KY R+41
- Signal Mountain, TN R+28
- North Auburn, CA R+13
- Rayne, LA R+49
- Jefferson Valley-Yorktown, NY R+8
- Mapleton, UT R+52
- Bound Brook, NJ D+17
- New Palestine, IN R+41
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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.