Somerville is a Democratic stronghold. About 84% of voters here vote Democratic and 16% Republican.
About 60% of adults in Somerville typically vote, near the U.S. average of about 62%. Among adults in Somerville, ~51% vote Democratic, ~9% Republican, and ~40% don't vote. The map below shows estimated turnout by block group.
How Somerville compares
Among cities within 25 miles, Somerville leans more Democratic than 146 of 151 neighbors.
Somerville runs about 44 points more Democratic than Massachusetts as a whole.
Politics vary noticeably by neighborhood within Somerville. The west side is the most Democratic-leaning (D+77) and the northeast side is the least Democratic-leaning (D+50), a spread of about 26 points.
Why Somerville 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 Somerville, not a ranked or complete list of what matters most.
Dense areas vote Democratic. More than 99% of residents in Somerville live in densely developed areas, about 63 points above the U.S. average of 36%. High college attainment predicts Democratic voting, and Somerville sits in the top quarter (about 70%, in the top fraction of cities). A high never-married share predicts Democratic voting, and about 59% of adults in Somerville have never been married, in the top fraction of cities.
Walkability and Democratic lean
Places with a highly walkable street grid tend to lean Democratic; Somerville, MA sits in the top tenth nationally on this measure. A walkable street grid does not change how people vote; it mostly reflects how urban a place is.
Why turnout in Somerville looks the way it does
Renters vote less often than owners. About 65% of households in Somerville rent, about 40 points above the U.S. average of 25%. Strong routine healthcare access lines up with higher turnout, and Somerville sits in the top quarter on routine-care measures. Learn more about the findings and methodology on the political spectrum map.
Nearby Cities
- Cambridge, MA D+74
- Medford, MA D+46
- Charlestown, MA D+53
- Allston, MA D+67
- Watertown, MA D+77
- Everett, MA D+25
- Arlington, MA D+69
- Belmont, MA D+63
- Malden, MA D+39
- Chelsea, MA D+31
Cities with Similar Populations
- Johns Creek, GA D+9
- Springdale, AR R+7
- Madera, CA Even
- Centennial, CO D+16
- Littleton, CO D+17
- Westland, MI D+15
- Mountain View, CA D+46
- Rancho Cordova, CA D+10
- Eau Claire, WI D+16
- Bloomington, IL D+11
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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.