Boston leans Democratic by roughly 30 points: about 65% of voters vote Democratic and 35% Republican.
About 71% of adults in the Boston area typically vote, above the U.S. average of about 62%. Among adults in the Boston area, ~46% vote Democratic, ~25% Republican, and ~29% don't vote. The map below shows estimated turnout by block group.
How Boston compares
Among cities within 25 miles, Boston leans more Democratic than 84 of 150 neighbors.
Boston runs about 7 points more Democratic than Massachusetts as a whole.
Politics vary noticeably by neighborhood within Boston. The south side is the most Democratic-leaning (D+47) and the north side is the least Democratic-leaning (D+9), a spread of about 38 points.
Why Boston leans the way it does
This analysis examined 14,881 data points per city to find what predicts political lean and turnout. The items below are a few correlations that stood out for Boston, not a ranked or complete list of what matters most.
Dense areas vote Democratic. About 78% of residents in the Boston area live in densely developed areas, about 42 points above the U.S. average of 36%. High college attainment predicts Democratic voting, and Boston sits in the top quarter (about 52%, above 94% of cities). A high never-married share predicts Democratic voting, and about 37% of adults in the Boston area have never been married, above 91% of cities.
Population density and Democratic lean
Places with high population density tend to lean Democratic; Boston, MA sits in the top tenth nationally on this measure.
Why turnout in Boston looks the way it does
Areas with strong routine healthcare access turn out at higher rates. Boston 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 71%, about 11 points above the U.S. average of 60%. Learn more about the findings and methodology on the political spectrum map.
Nearby Cities
- Jamaica Plain, MA D+71
- Brookline, MA D+72
- Charlestown, MA D+53
- Allston, MA D+67
- Cambridge, MA D+74
- Mattapan, MA D+74
- Somerville, MA D+69
- Brighton, MA D+61
- Roslindale, MA D+61
- Chelsea, MA D+31
Cities with Similar Populations
- Phoenix, AZ Even
- San Francisco, CA D+48
- Riverside, CA Even
- Detroit, MI D+13
- Seattle, WA D+30
- Atlanta, GA D+19
- Miami, FL D+4
- Minneapolis, MN D+19
- Philadelphia, PA D+27
- Washington, DC D+43
All Local Stats
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Sources and methodology
Precinct-level voting records used to fit the model come from Massachusetts Secretary of the Commonwealth, 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.