Port Costa leans heavily Democratic by roughly 36 points: about 68% of voters vote Democratic and 32% Republican.
About 48% of adults in Port Costa typically vote, below the U.S. average of about 62%. Among adults in Port Costa, ~33% vote Democratic, ~15% Republican, and ~52% don't vote. The map below shows estimated turnout by block group.
How Port Costa compares
Among cities within 25 miles, Port Costa leans more Democratic than 25 of 73 neighbors.
Port Costa runs about 16 points more Democratic than California as a whole.
Politics vary noticeably by neighborhood within Port Costa. The east side is the most Democratic-leaning (D+38) and the south side is the least Democratic-leaning (D+11), a spread of about 27 points.
Why Port Costa 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 Port Costa, not a ranked or complete list of what matters most.
Areas with high college attainment vote Democratic. About 41% of adults in Port Costa hold a bachelor's degree, about 13 points above the U.S. average of 28%.
Park access and Democratic lean
Places with heavy park coverage tend to lean Democratic; Port Costa, CA sits in the top tenth nationally on this measure. Park access does not change how people vote; it tends to track denser, higher-income areas.
Why turnout in Port Costa looks the way it does
Areas with strong routine healthcare access turn out at higher rates. Port Costa 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 70%, about 10 points above the U.S. average of 60%. Learn more about the findings and methodology on the political spectrum map.
Nearby Cities
- Crockett, CA D+40
- Benicia, CA D+15
- Rodeo, CA D+38
- Hercules, CA D+46
- Vallejo, CA D+38
- Martinez, CA D+30
- Pinole, CA D+39
- El Sobrante, CA D+46
- Reliez Valley, CA D+34
Cities with Similar Populations
- Houghton Lake Heights, MI R+35
- Polk, MO R+69
- Old Appleton, MO R+73
- Yellow Spring, WV R+62
- Harlingen, NJ D+22
- Duckrun, KY R+78
- Dodge, WI R+27
- Cobalt, ID R+69
- Alton Station, KY R+61
- Naper, NE R+75
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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.