99166 leans heavily Republican by roughly 46 points: about 27% of voters vote Democratic and 73% Republican.
About 69% of adults in 99166 typically vote, above the U.S. average of about 62%. Among adults in 99166, ~19% vote Democratic, ~50% Republican, and ~31% don't vote. The map below shows estimated turnout by block group.
How 99166 compares
99166 sits in a sparsely populated area with few comparable zip codes nearby.
99166 runs about 64 points more Republican than Washington as a whole. Washington leans Democratic overall, while 99166 is one of the few Republican-leaning pockets.
Politics vary noticeably by block within 99166. The east side is the most Republican-leaning (R+52) and the southwest side is the least Republican-leaning (R+38), a spread of about 14 points.
Why 99166 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 99166, not a ranked or complete list of what matters most.
99166 votes against the grain of Washington. Washington leans Democratic overall, while 99166 runs about 64 points more Republican. Rural areas vote Republican, and 99166 sits in the bottom quarter on density (about 4%, below 87% of zip codes). Low college attainment predicts Republican voting, and 99166 sits in the bottom quarter (about 14%, below 83% of zip codes).
Population density and Republican lean
Places with low population density tend to lean Republican; 99166, WA sits in the bottom quarter nationally on this measure.
Why turnout in 99166 looks the way it does
Turnout in 99166 sits close to the national pattern. Routine healthcare access, homeownership, education, and food security all land near their national averages here. 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 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.