Mercer Island leans heavily Democratic by roughly 50 points: about 75% of voters vote Democratic and 25% Republican.
About 82% of adults in Mercer Island typically vote, above the U.S. average of about 62%. Among adults in Mercer Island, ~61% vote Democratic, ~21% Republican, and ~18% don't vote. The map below shows estimated turnout by block group.
How Mercer Island compares
Among cities within 25 miles, Mercer Island leans more Democratic than 101 of 104 neighbors.
Mercer Island runs about 31 points more Democratic than Washington as a whole.
Why Mercer Island 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 Mercer Island, not a ranked or complete list of what matters most.
Areas with high college attainment vote Democratic. About 82% of adults in Mercer Island hold a bachelor's degree, about 53 points above the U.S. average of 28%. Dense areas vote Democratic, and Mercer Island sits in the top fifth on density (about 69%, above 92% of cities).
Walkability and Democratic lean
Places with a highly walkable street grid tend to lean Democratic; Mercer Island, WA 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 Mercer Island looks the way it does
Areas with strong routine healthcare access turn out at higher rates. Mercer Island 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 78%, about 18 points above the U.S. average of 60%. High high-school completion lines up with higher turnout, and about 98% of adults in Mercer Island have completed high school, above 96% of cities. Learn more about the findings and methodology on the political spectrum map.
Nearby Cities
- Beaux Arts Village, WA D+48
- Newcastle, WA D+43
- Bellevue, WA D+44
- Medina, WA D+29
- Clyde Hill, WA D+41
- Bryn Mawr-Skyway, WA D+48
- Hunts Point, WA D+37
- Yarrow Point, WA D+37
- Boulevard Park, WA D+34
- Seattle, WA D+30
Cities with Similar Populations
- Meadville, PA R+18
- Citrus Park, FL R+5
- Cockeysville, MD D+25
- Clarkston, GA D+57
- Drexel Heights, AZ D+23
- San Lorenzo, CA D+34
- Soledad, CA D+22
- Albemarle, NC R+34
- Warrensburg, MO R+19
- Hazelwood, MO D+37
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.