83604 is a Republican stronghold. About 17% of voters here vote Democratic and 83% Republican.
About 52% of adults in 83604 typically vote, below the U.S. average of about 62%. Among adults in 83604, ~9% vote Democratic, ~43% Republican, and ~48% don't vote. The map below shows estimated turnout by block group.
How 83604 compares
83604 runs about 31 points more Republican than Idaho as a whole.
Politics vary noticeably by block within 83604. The north side is the most Republican-leaning (R+76) and the northwest side is the least Republican-leaning (R+54), a spread of about 21 points.
Why 83604 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 83604, not a ranked or complete list of what matters most.
Rural areas vote Republican. Fewer than 1% of residents in 83604 live in densely developed areas, about 17 points below the Idaho average of 18%. Low college attainment predicts Republican voting, and 83604 sits in the bottom quarter (about 13%, below 88% of zip codes).
Population density and Republican lean
Places with low population density tend to lean Republican; 83604, ID sits in the bottom tenth nationally on this measure.
Why turnout in 83604 looks the way it does
Areas with limited routine healthcare access turn out at lower rates. 83604 is in the bottom quarter nationally for routine-care measures such as insurance coverage, preventive screenings, and dental visits. Renters vote less often than owners, and about 37% of households in 83604 rent, above 84% of zip codes. High-crime urban areas turn out at lower rates, and 83604 sits in the top 15% on a violent-crime measure. 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 Idaho 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.