02421 is a Democratic stronghold. About 78% of voters here vote Democratic and 22% Republican.
About 84% of adults in 02421 typically vote, above the U.S. average of about 62%. Among adults in 02421, ~66% vote Democratic, ~18% Republican, and ~16% don't vote. The map below shows estimated turnout by block group.
How 02421 compares
Among zip codes within 15 miles, 02421 leans more Democratic than 69 of 110 neighbors.
02421 runs about 31 points more Democratic than Massachusetts as a whole.
Politics vary noticeably by block within 02421. The northeast side is the most Democratic-leaning (D+62) and the southwest side is the least Democratic-leaning (D+50), a spread of about 12 points.
Why 02421 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 02421, not a ranked or complete list of what matters most.
Areas with high college attainment vote Democratic. About 84% of adults in 02421 hold a bachelor's degree, about 55 points above the U.S. average of 28%. Dense areas vote Democratic, and 02421 sits in the top fifth on density (about 79%, above 82% of zip codes).
Population density and Democratic lean
Places with high population density tend to lean Democratic; 02421, MA sits in the top quarter nationally on this measure.
Why turnout in 02421 looks the way it does
Areas with strong routine healthcare access turn out at higher rates. 02421 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 80%, about 20 points above the U.S. average of 60%. High high-school completion lines up with higher turnout, and about 96% of adults in 02421 have completed high school, above 84% 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 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.