78663 is a Republican stronghold. About 25% of voters here vote Democratic and 75% Republican.
About 68% of adults in 78663 typically vote, above the U.S. average of about 62%. Among adults in 78663, ~17% vote Democratic, ~51% Republican, and ~32% don't vote. The map below shows estimated turnout by block group.
How 78663 compares
Among zip codes within 15 miles, 78663 leans more Republican than 3 of 4 neighbors.
78663 runs about 37 points more Republican than Texas as a whole.
Politics vary noticeably by block within 78663. The west side is the most Republican-leaning (R+56) and the southeast side is the least Republican-leaning (R+39), a spread of about 17 points.
Why 78663 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 78663, not a ranked or complete list of what matters most.
Areas with many family households vote Republican. About 76% of households in 78663 are family households, about 9 points above the U.S. average of 67%.
Paved land cover and Republican lean
Places with little paved surface tend to lean Republican; 78663, TX sits in the bottom tenth nationally on this measure. Paved ground does not change how people vote; it mostly reflects how urban and built-up a place is.
Why turnout in 78663 looks the way it does
Areas with strong routine healthcare access turn out at higher rates. 78663 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 65%, about 5 points above the U.S. average of 60%. High high-school completion lines up with higher turnout, and about 98% of adults in 78663 have completed high school, above 94% of zip codes. 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.