Mercer County leans Republican by roughly 26 points: about 37% of voters vote Democratic and 63% Republican.
About 75% of adults in Mercer County typically vote, above the U.S. average of about 62%. Among adults in Mercer County, ~28% vote Democratic, ~47% Republican, and ~25% don't vote. The map below shows estimated turnout by block group.
How Mercer County compares
Among counties within 50 miles, Mercer County leans more Republican than 4 of 12 neighbors.
Mercer County runs about 25 points more Republican than Pennsylvania as a whole.
Politics vary noticeably by city within Mercer County. The southwest side runs the most Democratic (D+4) and the northeast side runs the most Republican (R+57), a spread of about 60 points.
Why Mercer County leans the way it does
This analysis examined 14,881 data points per county to find what predicts political lean and turnout. The items below are a few correlations that stood out for Mercer County, not a ranked or complete list of what matters most.
Mercer County votes Republican even though it is densely developed (about 50%, well above the Pennsylvania average of 33%). State and regional patterns outweigh the Democratic lean that density usually predicts here.
Paved land cover and Democratic lean
Places with extensive paved surfaces tend to lean Democratic; Mercer County, PA sits above the national average 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 Mercer County looks the way it does
Turnout in Mercer County 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 Counties
- Lawrence County, PA R+28
- Trumbull County, OH R+17
- Mahoning County, OH Even
- Crawford County, PA R+39
- Venango County, PA R+42
- Butler County, PA R+28
- Columbiana County, OH R+45
- Beaver County, PA R+19
- Ashtabula County, OH R+32
- Clarion County, PA R+50
Counties with Similar Populations
- Hardin County, KY R+27
- Cowlitz County, WA R+18
- Androscoggin County, ME R+12
- Douglas County, OR R+29
- Craighead County, AR R+27
- Hanover County, VA R+21
- LaSalle County, IL R+21
- Warren County, NJ R+16
- Terrebonne Parish, LA R+42
- Delaware County, IN R+11
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.