Altadena is a Democratic stronghold. About 79% of voters here vote Democratic and 21% Republican.
About 73% of adults in Altadena typically vote, above the U.S. average of about 62%. Among adults in Altadena, ~58% vote Democratic, ~15% Republican, and ~27% don't vote. The map below shows estimated turnout by block group.
How Altadena compares
Among cities within 25 miles, Altadena leans more Democratic than 120 of 125 neighbors.
Altadena runs about 39 points more Democratic than California as a whole.
Politics vary noticeably by neighborhood within Altadena. The north side is the most Democratic-leaning (D+65) and the southeast side is the least Democratic-leaning (D+44), a spread of about 22 points.
Why Altadena 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 Altadena, not a ranked or complete list of what matters most.
Dense areas vote Democratic. About 91% of residents in Altadena live in densely developed areas, about 55 points above the U.S. average of 36%. High college attainment predicts Democratic voting, and Altadena sits in the top quarter (about 54%, above 95% of cities). A high never-married share predicts Democratic voting, and about 33% of adults in Altadena have never been married, above 82% of cities.
Walkability and Democratic lean
Places with a highly walkable street grid tend to lean Democratic; Altadena, CA sits in the top tenth 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 Altadena looks the way it does
Areas with strong routine healthcare access turn out at higher rates. Altadena 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
- Pasadena, CA D+51
- Kinneloa Mesa, CA D+16
- La Canada Flintridge, CA D+19
- San Marino, CA D+21
- East Pasadena, CA D+33
- Sierra Madre, CA D+30
- Montrose, CA D+15
- South Pasadena, CA D+52
- La Crescenta-Montrose, CA D+16
- Glendale, CA D+13
Cities with Similar Populations
- Fenton, MI R+20
- Lewiston, ME D+9
- Pacifica, CA D+43
- Bay Shore, NY D+7
- West Babylon, NY R+7
- Cibolo, TX R+11
- Addison, IL D+3
- North Bay Village, FL R+5
- Stow, OH Even
- Willis, TX R+43
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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.