Lewis and Clark County leans slightly Republican by roughly 8 points: about 46% of voters vote Democratic and 54% Republican.
About 87% of adults in Lewis and Clark County typically vote, above the U.S. average of about 62%. Among adults in Lewis and Clark County, ~40% vote Democratic, ~47% Republican, and ~13% don't vote. The map below shows estimated turnout by block group.
How Lewis and Clark County compares
Among counties within 50 miles, Lewis and Clark County is the least Republican-leaning.
Lewis and Clark County runs about 13 points more Democratic than Montana as a whole.
Politics vary noticeably by city within Lewis and Clark County. The south side runs the most Democratic (D+35) and the northwest side runs the most Republican (R+48), a spread of about 83 points.
Why Lewis and Clark County leans the way it does
This analysis examined 14,881 data points per county to find what predicts political lean and turnout. The items below are a few correlations that stood out for Lewis and Clark County, not a ranked or complete list of what matters most.
Lewis and Clark County votes Republican even though it is densely developed (about 54%, far above the Montana average of 13%). State and regional patterns outweigh the Democratic lean that density usually predicts here.
Food insecurity and voter turnout
Places with low food insecurity tend to turn out at a higher rate; Lewis and Clark County, MT sits in the bottom tenth nationally on this measure. Food insecurity does not directly drive turnout; it reflects economic hardship, which lines up with lower voting.
Why turnout in Lewis and Clark County looks the way it does
Areas with strong routine healthcare access turn out at higher rates. Lewis and Clark 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 67%, about 7 points above the U.S. average of 60%. High high-school completion lines up with higher turnout, and about 95% of adults in Lewis and Clark County have completed high school, above 89% of counties. Learn more about the findings and methodology on the political spectrum map.
Nearby Counties
- Jefferson County, MT R+38
- Broadwater County, MT R+54
- Powell County, MT R+48
- Silver Bow County, MT Even
- Meagher County, MT R+58
- Deer Lodge County, MT R+18
- Granite County, MT R+38
- Cascade County, MT R+25
- Teton County, MT R+60
- Gallatin County, MT D+6
Counties with Similar Populations
- Franklin County, MA D+22
- Boone County, IN R+19
- Surry County, NC R+52
- Portage County, WI R+7
- DeKalb County, AL R+71
- Creek County, OK R+55
- Morgan County, IN R+51
- Greene County, TN R+62
- York County, VA R+3
- Riley County, KS D+4
Sources and methodology
Precinct-level voting records used to fit the model come from Montana 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.