Jefferson County is a true toss-up. About 48% of voters here vote Democratic and 52% Republican.
About 93% of adults in Jefferson County typically vote, above the U.S. average of about 62%. Among adults in Jefferson County, ~45% vote Democratic, ~48% Republican, and ~7% don't vote. The map below shows estimated turnout by block group.
How Jefferson County compares
Among counties within 50 miles, Jefferson County is the least Republican-leaning.
Jefferson County runs about 10 points more Democratic than Iowa as a whole.
Politics vary noticeably by city within Jefferson County. The north side runs the most Democratic (D+10) and the northeast side runs the most Republican (R+46), a spread of about 56 points.
Why Jefferson County leans the way it does
Density, race composition, education, and family structure all sit close to their national averages in Jefferson County. The lean here lands roughly where demographic data alone would predict.
High-school completion, uninsured rate, and voter turnout
Places that combine high-school-completion-heavy adults and a low uninsured rate tend to turn out at a higher rate, as Jefferson County, IA does.
Why turnout in Jefferson County looks the way it does
Areas with strong routine healthcare access turn out at higher rates. Jefferson 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 66%, about 6 points above the U.S. average of 60%. High high-school completion lines up with higher turnout, and about 95% of adults in Jefferson County have completed high school, above 93% of counties. Learn more about the findings and methodology on the political spectrum map.
Nearby Counties
- Van Buren County, IA R+55
- Henry County, IA R+31
- Wapello County, IA R+26
- Keokuk County, IA R+47
- Washington County, IA R+33
- Davis County, IA R+59
- Louisa County, IA R+37
- Scotland County, MO R+64
- Mahaska County, IA R+38
- Lee County, IA R+27
Counties with Similar Populations
- Pemiscot County, MO R+30
- Henry County, KY R+51
- Nottoway County, VA R+9
- Aitkin County, MN R+33
- Mercer County, IL R+33
- Floyd County, IA R+30
- Carroll County, IL R+34
- Jefferson County, GA D+5
- Clarke County, MS R+26
- Grand County, CO R+6
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.