Foster City leans heavily Democratic by roughly 50 points: about 75% of voters vote Democratic and 25% Republican.
About 63% of adults in Foster City typically vote, near the U.S. average of about 62%. Among adults in Foster City, ~47% vote Democratic, ~16% Republican, and ~37% don't vote. The map below shows estimated turnout by block group.
How Foster City compares
Among cities within 25 miles, Foster City leans more Democratic than 48 of 73 neighbors.
Foster City runs about 29 points more Democratic than California as a whole.
Why Foster City 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 Foster City, not a ranked or complete list of what matters most.
Dense areas vote Democratic. About 89% of residents in Foster City live in densely developed areas, about 53 points above the U.S. average of 36%. High college attainment predicts Democratic voting, and Foster City sits in the top quarter (about 74%, in the top fraction of cities).
Population density and Democratic lean
Places with high population density tend to lean Democratic; Foster City, CA sits in the top tenth nationally on this measure.
Why turnout in Foster City looks the way it does
Areas with strong routine healthcare access turn out at higher rates. Foster City 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 73%, about 13 points above the U.S. average of 60%. High high-school completion lines up with higher turnout, and about 96% of adults in Foster City have completed high school, above 86% of cities. Learn more about the findings and methodology on the political spectrum map.
Nearby Cities
- San Mateo, CA D+49
- Belmont, CA D+53
- San Carlos, CA D+57
- Highlands-Baywood Park, CA D+52
- Hillsborough, CA D+41
- Redwood City, CA D+53
- Burlingame, CA D+52
- North Fair Oaks, CA D+49
- Atherton, CA D+46
- Menlo Park, CA D+64
Cities with Similar Populations
- Pasadena, MD R+12
- Reisterstown, MD D+28
- University Park, FL R+33
- Fair Oaks, VA D+40
- Placerville, CA R+21
- Boone, NC D+20
- Ambler, PA D+25
- Williston, ND R+58
- Melrose Park, IL D+22
- Troy, OH R+33
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.