Snohomish County leans slightly Democratic by roughly 10 points: about 55% of voters vote Democratic and 45% Republican.
About 74% of adults in Snohomish County typically vote, above the U.S. average of about 62%. Among adults in Snohomish County, ~41% vote Democratic, ~33% Republican, and ~26% don't vote. The map below shows estimated turnout by block group.
How Snohomish County compares
Among counties within 50 miles, Snohomish County leans more Democratic than 1 of 5 neighbors.
Snohomish County runs about 8 points more Republican than Washington as a whole.
Politics vary noticeably by city within Snohomish County. The southwest side runs the most Democratic (D+25) and the northwest side runs the most Republican (R+14), a spread of about 39 points.
Why Snohomish 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 Snohomish County, not a ranked or complete list of what matters most.
Dense areas vote Democratic. About 80% of residents in Snohomish County live in densely developed areas, about 44 points above the U.S. average of 36%. High college attainment predicts Democratic voting, and Snohomish County sits in the top quarter (about 38%, above 90% of counties).
Paved land cover and Democratic lean
Places with extensive paved surfaces tend to lean Democratic; Snohomish County, WA sits in the top tenth nationally 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 Snohomish County looks the way it does
Areas with strong routine healthcare access turn out at higher rates. Snohomish County 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 67%, about 6 points above the U.S. average of 60%. Learn more about the findings and methodology on the political spectrum map.
Nearby Counties
- King County, WA D+45
- Island County, WA D+10
- Jefferson County, WA D+45
- Kitsap County, WA D+18
- Skagit County, WA D+4
- Pierce County, WA D+12
- San Juan County, WA D+50
- Clallam County, WA D+9
- Mason County, WA R+5
- Whatcom County, WA D+23
Counties with Similar Populations
- Hamilton County, OH D+21
- Fort Bend County, TX D+6
- Multnomah County, OR D+52
- Ventura County, CA D+16
- Essex County, MA D+18
- Baltimore County, MD D+28
- Montgomery County, PA D+21
- Suffolk County, MA D+53
- Oklahoma County, OK D+6
- Worcester County, MA D+12
Sources and methodology
Precinct-level voting records used to fit the model come from Washington Secretary of State, 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.