78109 leans Democratic by roughly 16 points: about 58% of voters vote Democratic and 42% Republican.
About 54% of adults in 78109 typically vote, below the U.S. average of about 62%. Among adults in 78109, ~31% vote Democratic, ~23% Republican, and ~46% don't vote. The map below shows estimated turnout by block group.
How 78109 compares
Among zip codes within 15 miles, 78109 leans more Democratic than 21 of 41 neighbors.
78109 runs about 30 points more Democratic than Texas as a whole. Texas leans Republican overall, while 78109 is one of the few Democratic-leaning pockets.
Politics vary noticeably by block within 78109. The northeast side runs the most Democratic (D+29) and the southeast side runs the most Republican (R+10), a spread of about 39 points.
Why 78109 leans the way it does
This analysis examined 14,881 data points per zip code to find what predicts political lean and turnout. The items below are a few correlations that stood out for 78109, not a ranked or complete list of what matters most.
Dense areas vote Democratic. About 77% of residents in 78109 live in densely developed areas, about 41 points above the U.S. average of 36%. 78109 runs against the grain of Texas, a Democratic-leaning pocket in a Republican-leaning state.
Walkability and Democratic lean
Places with a highly walkable street grid tend to lean Democratic; 78109, TX 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 78109 looks the way it does
Areas with limited routine healthcare access turn out at lower rates. 78109 is in the bottom quarter nationally for routine-care measures such as insurance coverage, preventive screenings, and dental visits. Learn more about the findings and methodology on the political spectrum map.
Nearby Zip Codes
Zip Codes with Similar Populations
Sources and methodology
Precinct-level voting records used to fit the model come from Texas Secretary of State, Elections Division, 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.