15204 leans heavily Democratic by roughly 48 points: about 74% of voters vote Democratic and 26% Republican.
About 63% of adults in 15204 typically vote, near the U.S. average of about 62%. Among adults in 15204, ~47% vote Democratic, ~16% Republican, and ~37% don't vote. The map below shows estimated turnout by block group.
How 15204 compares
Among zip codes within 15 miles, 15204 leans more Democratic than 75 of 91 neighbors.
15204 runs about 50 points more Democratic than Pennsylvania as a whole. Pennsylvania is roughly evenly split, and 15204 sits clearly on the Democratic side.
Politics vary noticeably by block within 15204. The east side is the most Democratic-leaning (D+60) and the south side is the least Democratic-leaning (D+29), a spread of about 30 points.
Why 15204 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 15204, not a ranked or complete list of what matters most.
Dense areas vote Democratic. About 93% of residents in 15204 live in densely developed areas, about 56 points above the U.S. average of 36%. A high never-married share predicts Democratic voting, and about 45% of adults in 15204 have never been married, above 92% of zip codes. 15204 runs against the grain of Pennsylvania, a Democratic-leaning outlier in a roughly evenly split state.
Paved land cover and Democratic lean
Places with extensive paved surfaces tend to lean Democratic; 15204, PA sits in the top quarter 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 15204 looks the way it does
Turnout in 15204 sits close to the national pattern. Routine healthcare access, homeownership, education, and food security all land near their national averages here. 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.