Diablo leans Democratic by roughly 16 points: about 58% of voters vote Democratic and 42% Republican.
About 83% of adults in Diablo typically vote, above the U.S. average of about 62%. Among adults in Diablo, ~48% vote Democratic, ~35% Republican, and ~17% don't vote. The map below shows estimated turnout by block group.
How Diablo compares
Among cities within 25 miles, Diablo leans more Democratic than 11 of 61 neighbors.
Diablo runs about 5 points more Republican than California as a whole.
Politics vary noticeably by neighborhood within Diablo. The south side runs the most Democratic (D+18) and the northeast side runs the most Republican (R+2), a spread of about 20 points.
Why Diablo 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 Diablo, not a ranked or complete list of what matters most.
Areas with high college attainment vote Democratic. About 75% of adults in Diablo hold a bachelor's degree, about 47 points above the U.S. average of 28%. Dense areas vote Democratic, and Diablo sits in the top fifth on density (about 60%, above 90% of cities).
Population density, never-married share, and Democratic lean
Places that combine high population density and a low never-married share tend to lean Democratic, as Diablo, CA does.
Why turnout in Diablo looks the way it does
Areas with strong routine healthcare access turn out at higher rates. Diablo 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 78%, about 18 points above the U.S. average of 60%. Homeowners vote more often than renters, and about 91% of households in Diablo own their home, about 15 points above the U.S. average of 75%. High high-school completion lines up with higher turnout, and about 99% of adults in Diablo have completed high school, above 98% of cities. Learn more about the findings and methodology on the political spectrum map.
Nearby Cities
- Danville, CA D+27
- Alamo, CA D+20
- San Ramon, CA D+34
- Castle Hill, CA D+41
- Clayton, CA D+14
- Walnut Creek, CA D+47
- Concord, CA D+33
- Lafayette, CA D+48
- Moraga, CA D+49
- Dublin, CA D+35
Cities with Similar Populations
- Chatham, LA R+62
- Stovall, NC R+19
- Copake, NY D+13
- Santa Anna, TX R+70
- Loveville, MD R+24
- Cedarview, UT R+84
- Grays Prairie, TX R+68
- Ladd, IL R+24
- Redwater, TX R+79
- Mangum, MI Even
All Local Stats
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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.