King County leans heavily Democratic by roughly 46 points: about 73% of voters vote Democratic and 27% Republican.
About 70% of adults in King County typically vote, above the U.S. average of about 62%. Among adults in King County, ~51% vote Democratic, ~19% Republican, and ~30% don't vote. The map below shows estimated turnout by block group.
How King County compares
Among counties within 50 miles, King County is the most Democratic-leaning.
King County runs about 27 points more Democratic than Washington as a whole.
Politics vary noticeably by city within King County. The northwest side is the most Democratic-leaning (D+69) and the southeast side is the least Democratic-leaning (D+18), a spread of about 51 points.
Why King 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 King County, not a ranked or complete list of what matters most.
Dense areas vote Democratic. About 87% of residents in King County live in densely developed areas, about 51 points above the U.S. average of 36%. High college attainment predicts Democratic voting, and King County sits in the top quarter (about 56%, in the top fraction of counties). A high never-married share predicts Democratic voting, and about 36% of adults in King County have never been married, above 86% of counties.
Population density and Democratic lean
Places with high population density tend to lean Democratic; King County, WA sits in the top tenth nationally on this measure.
Why turnout in King County looks the way it does
Areas with strong routine healthcare access turn out at higher rates. King 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 70%, about 10 points above the U.S. average of 60%. High high-school completion lines up with higher turnout, and about 94% of adults in King County have completed high school, above 81% of counties. Learn more about the findings and methodology on the political spectrum map.
Nearby Counties
- Kitsap County, WA D+18
- Snohomish County, WA D+10
- Pierce County, WA D+12
- Mason County, WA R+5
- Jefferson County, WA D+45
- Thurston County, WA D+19
- Island County, WA D+10
- Skagit County, WA D+4
- Clallam County, WA D+9
- Lewis County, WA R+29
Counties with Similar Populations
- Clark County, NV D+12
- San Bernardino County, CA Even
- Queens County, NY D+23
- Riverside County, CA Even
- Tarrant County, TX D+3
- Bexar County, TX D+14
- Broward County, FL D+20
- Santa Clara County, CA D+32
- Dallas County, TX D+27
- Miami-Dade County, FL R+8
All Local Stats
Home Services
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.