- Lead
- 5,706
- Total
- 25,097
- vs nation
- D+24.2
Idaho 18th State Senate District
President margin by year
Place winner margin
President results by year
Modeled candidate-vote estimate on current district boundaries
- Lead
- 6,755
- Total
- 26,493
- vs nation
- D+21.0
- Lead
- 3,343
- Total
- 21,059
- vs nation
- D+13.8
- Lead
- 3,300
- Total
- 19,604
- vs nation
- D+13.0
- Lead
- 4,352
- Total
- 19,820
- vs nation
- D+14.7
- Lead
- 795
- Total
- 16,125
- vs nation
- D+7.4
- Lead
- 179
- Total
- 12,609
- vs nation
- R+1.9
- Lead
- 1,209
- Total
- 12,469
- vs nation
- D+1.2
Key facts
- 2024 presidential margin
- D+22.7MIT Election Lab
- Population
- 51,9482024 5-year
- Population density
- 372 / sq mi2024 5-year · TIGER/Line
- Land area
- 140 sq miTIGER/Line
- Median household income
- $100,1402024 5-year
- White (non-Hispanic)
- 78.6%2024 5-year
- Black
- 1.3%2024 5-year
- Hispanic / Latino
- 8.2%2024 5-year
- Peak Democratic margin
- D+53.9 in 1896MIT Election Lab
- Peak Republican margin
- R+35.8 in 1892MIT Election Lab
- Most similar
- State Senate District 16, ID · twin score 89.8
presidential history
Party record book
Idaho 18th State Senate District · the strongest Democratic and Republican presidential performances recorded here, measured three ways.
1892–2024 · 34 presidential cycles
Highest vote share
Largest share of the presidential candidate vote cast here.
Democratic
William J. Bryan1896
76.9%
247 votes · D+53.9 · modeled estimate
Runner-up · Franklin D. Roosevelt, 1936 · 71.7%
Republican
Ronald Reagan1984
59.5%
4,793 votes · R+20.6 · modeled estimate
Runner-up · Dwight D. Eisenhower, 1952 · 59.4%
Most votes
Largest number of votes cast for the party’s presidential nominee here.
Democratic
Joe Biden2020
16,190votes
61.1% of the vote · D+25.5 · modeled estimate
Runner-up · Kamala Harris, 2024 · 14,986 votes
Republican
Donald Trump2020
9,435votes
35.6% of the vote · D+25.5 · modeled estimate
Runner-up · Donald Trump, 2024 · 9,280 votes
Best relative to the U.S.
This Place’s margin against the national margin in the same election — positive when it leaned toward the party more than the country did.
Democratic
William J. Bryan1896
+60.0pts D vs U.S.
Place D+53.9 · U.S. R+6.1 · modeled estimate
Runner-up · William J. Bryan, 1908 · +30.6 pts
Republican
Benjamin Harrison1892
+37.5pts R vs U.S.
Place R+35.8 · U.S. D+1.7 · a third-party candidate carried the Place · modeled estimate
Runner-up · Richard Nixon, 1968 · +15.1 pts
Current officeholders
State legislative officeholder from OpenStates nightly current-legislator data.
Senate and governor results are in the Office selector at the top of this page.
U.S. House
Each row is a county-allocated estimate of U.S. House votes for this district — county returns apportioned onto its boundary, not precinct-counted. “Vote lead” is the estimated local lead here, not necessarily the winner of the full contest.
Idaho Senate District 18 covers a dense slice of Ada County where the 2024 presidential margin reached D+22.8 — an outlier in a state that leans heavily Republican statewide, reflecting the district's younger, college-educated urban electorate.
Across the recorded series it reached a Democratic high of 53.9 points in 1896 and a Republican high of 35.8 points in 1892. Between 2020 and 2024 the district moved 2.8 points toward the Republican candidate; the 2024 margin was 22.7 points.
A population of 51,948, a 79% non-Hispanic-white share, and a median household income of $100,140 describe the district. The district's voting pattern over the last decade is most similar to that of State Senate District 16 and State Senate District 17.
The state-senate districts whose fingerprint — 2000–2024 trajectory, demographics, ancestry, religion — sits closest to this one, and why.
Twin score (0–100) = weighted cosine between tier-standardized fingerprints: presidential margins 2000–2024 with 12-yr trend and elasticity, ACS income, age, education, population and race, top reported ancestries, and religious adherence — chips name the closest-shared dimensions and the widest gap. Re-weight the groups in the twins explorer.
District research tools
Open the source-auditable district brief for electoral baseline, electorate, current-cycle coverage, geography, official dates, and methodology. Open campaign intelligence report → · Browse all comparisons →
Idaho 18th State Senate District. Akashic. https://akashic.app/sld-upper/16018/. Accessed May 20, 2026. License: CC BY 4.0.