15904 leans heavily Republican by roughly 30 points: about 35% of voters vote Democratic and 65% Republican.
About 79% of adults in 15904 typically vote, above the U.S. average of about 62%. Among adults in 15904, ~28% vote Democratic, ~52% Republican, and ~20% don't vote. The map below shows estimated turnout by block group.
How 15904 compares
Among zip codes within 15 miles, 15904 leans more Republican than 4 of 36 neighbors.
15904 runs about 29 points more Republican than Pennsylvania as a whole.
Politics vary noticeably by block within 15904. The northeast side is the most Republican-leaning (R+40) and the west side is the least Republican-leaning (R+24), a spread of about 16 points.
Why 15904 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 15904, not a ranked or complete list of what matters most.
15904 votes Republican even though it is densely developed (about 66%, far above the Pennsylvania average of 33%). Here an older population outweighs the Democratic lean that density usually predicts.
Preventive-care access and voter turnout
Places with strong routine preventive-care access tend to turn out at a higher rate; 15904, PA sits in the top quarter nationally on this measure. Dental visits do not drive turnout; the rate reflects income, insurance, and healthcare access, which line up with who votes.
Why turnout in 15904 looks the way it does
Areas with strong routine healthcare access turn out at higher rates. 15904 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 68%, about 8 points above the U.S. average of 60%. High high-school completion lines up with higher turnout, and about 96% of adults in 15904 have completed high school, above 83% 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 Pennsylvania Department of State, Bureau of 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.