Portsmouth is a Republican stronghold. About 21% of voters here vote Democratic and 79% Republican.
About 81% of adults in Portsmouth typically vote, above the U.S. average of about 62%. Among adults in Portsmouth, ~17% vote Democratic, ~64% Republican, and ~19% don't vote. The map below shows estimated turnout by block group.
How Portsmouth compares
Among cities within 25 miles, Portsmouth leans more Republican than 35 of 38 neighbors.
Portsmouth runs about 44 points more Republican than Iowa as a whole.
Why Portsmouth 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 Portsmouth, not a ranked or complete list of what matters most.
Areas with many family households vote Republican. About 79% of households in Portsmouth are family households, about 13 points above the U.S. average of 67%.
Preventive-care access and voter turnout
Places with strong routine preventive-care access tend to turn out at a higher rate; Portsmouth, IA sits above the national average on this measure. Dental visits do not drive turnout; the rate reflects income, insurance, and healthcare access, which line up with who votes.
Why turnout in Portsmouth looks the way it does
Turnout in Portsmouth 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 Cities
- Panama, IA R+57
- Persia, IA R+50
- Tennant, IA R+54
- Westphalia, IA R+54
- Shelby, IA R+54
- Woodbine, IA R+45
- Earling, IA R+55
- Harlan, IA R+42
- Logan, IA R+44
- Minden, IA R+48
Cities with Similar Populations
- Adamsville, TX R+72
- Sylvan, PA R+67
- Wales, UT R+75
- Riddleville, GA R+10
- Long Lake, TX R+70
- Patmos, AR R+70
- Amador City, CA R+29
- Dix, NE R+73
- Trenholm, VA R+37
- Rougon, LA R+56
Sources and methodology
Precinct-level voting records used to fit the model come from Iowa 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.