Onset leans slightly Democratic by roughly 8 points: about 54% of voters vote Democratic and 46% Republican.
About 90% of adults in Onset typically vote, above the U.S. average of about 62%. Among adults in Onset, ~49% vote Democratic, ~41% Republican, and ~10% don't vote. The map below shows estimated turnout by block group.
How Onset compares
Among cities within 25 miles, Onset leans more Democratic than 54 of 94 neighbors.
Onset runs about 17 points more Republican than Massachusetts as a whole.
Why Onset 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 Onset, not a ranked or complete list of what matters most.
Dense areas vote Democratic. About 47% of residents in Onset live in densely developed areas, about 10 points above the U.S. average of 36%.
Population density and Democratic lean
Places with high population density tend to lean Democratic; Onset, MA sits in the top quarter nationally on this measure.
Why turnout in Onset looks the way it does
Areas with strong routine healthcare access turn out at higher rates. Onset 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 68%, about 8 points above the U.S. average of 60%. High high-school completion lines up with higher turnout, and about 99% of adults in Onset have completed high school, above 98% of cities. Learn more about the findings and methodology on the political spectrum map.
Nearby Cities
- East Wareham, MA R+4
- Wareham Center, MA Even
- Buzzards Bay, MA D+6
- Wareham, MA R+10
- Monument Beach, MA D+12
- White Island Shores, MA R+4
- Pocasset, MA D+17
- Bournedale, MA D+4
- Marion, MA D+14
Cities with Similar Populations
- Williamstown, NY R+50
- West Valley, NY R+43
- Simmesport, LA R+12
- Geraldine, AL R+81
- Hazelhurst, WI R+16
- Idria, CA R+19
- Loyall, KY R+61
- Rib Lake, WI R+51
- Plentywood, MT R+57
- Livermore, ME R+36
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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.