Short Answer

Jim Risch is expected to win the Idaho Senate seat in 2026, an outcome the market prices at 96.0%.

1. Market Behavior & Drivers

The market for the Idaho Senate election has remained stable, pricing in a high probability of a Republican victory from its inception. The most significant development, incumbent Senator Jim Risch securing the Republican primary on May 19, 2026, with 67.26% of the vote, produced no material change in pricing. The subsequent withdrawal of the Democratic candidate also failed to move the market.
This lack of volatility suggests traders had fully discounted the primary's outcome. The market has consistently traded in a narrow band between 0.1% and 2.0%, reflecting the consensus view that the incumbent faces no serious electoral threat in the general election. Total volume of 2,215 contracts underscores the low level of speculative interest in a non-Republican outcome.
  • Since last update (~28d): David Roth's odds declined by -1.1pp model-led, widening the edge by -0.6pp.
  • Jim Risch's model probability for winning increased by +1.7pp.
  • Our confidence in the prediction strengthened significantly, rising by +4.0pp.
  • Todd Achilles' model probability decreased by -0.7pp; market declined -1.0pp.
  • Incumbent Republican Jim Risch is heavily favored, with forecasters rating his Idaho seat Safe Republican.
  • Todd Achilles gained momentum after Roth's August 2026 withdrawal, yet Risch holds significant leads.

Who Wins and Why

Outcome Market Model Why
David Roth 1.4% 0.8% Democratic candidate David Roth officially withdrew from the race, diminishing the party's prospects.
Jim Risch 96.0% 94.9% Incumbent Republican Jim Risch won his primary and is heavily favored, with the seat rated "Safe Republican."
Todd Achilles 4.0% 4.3% David Roth's withdrawal cleared a path for independent Todd Achilles, and one survey indicated Achilles leading.

Current Context

Senator Jim Risch secured the Republican primary; the Democratic candidate withdrew. Incumbent Republican U.S. Senator Jim Risch, first elected in 2009, won his party's May 19, 2026, primary election with 67.26% of the vote [1][2][3][4][5]. David Roth won the Democratic primary on the same date [4][5], but withdrew from the U.S. Senate race on August 28, 2026 [6][7][8]. Roth's withdrawal officially removed him from the general election ballot [6][7][8].
Incumbent Senator Risch faces three challengers in a race rated "Safe Republican." The 2026 U.S. Senate general election in Idaho is scheduled for November 3, 2026 [6][7][9][4][5]. As of September 9, 2026, the election has not yet taken place [4][5]. The current general election ballot features incumbent Jim Risch (Republican), independent Todd Achilles, independent Natalie Fleming, and Libertarian Matt Loesby [6][7][9][4][5]. Recent polling suggests Senator Risch maintains a substantial lead over his challengers [9][10]. Election forecasters consistently rate the seat as safely Republican [9]. Decision Desk HQ, as of September 1, 2026, forecasts the race as "Safe Republican" with a 99% win probability for Senator Risch [5].
Sources (10)
  1. 1State Election Resultsresults.voteidaho.gov
  2. 2Idaho Senate Primary Election 2026 Live Resultsnbcnews.com
  3. 3Results by County | Election Resultsresults.voteidaho.gov
  4. 4United States Senate election in Idaho, 2026 - Ballotpediaballotpedia.org
  5. 52026 Idaho US Senate Forecast | DDHQvotes.decisiondeskhq.com
  6. 6Idaho US Senate candidate David Roth removes name from general election ballotyahoo.com
  7. 7Democrat David Roth to withdraw from Idaho Senate race, leaving independent Todd Achilles to face GOP Sen. Jim Rischspokesman.com
  8. 8Democratic candidate David Roth ends U.S. Senate bid, putting Risch and Achilles at forefront | Idaho State Election Coverage | idahopress.comidahopress.com
  9. 9Risch Holds Commanding Lead in Idaho Senate Race | Politics406.compolitics406.com
  10. 10Is this the most competitive race for Idaho US Senate seat in a half-century? It depends on which candidate you ask - East Idaho Newseastidahonews.com

2. Price Chart

Historical Price (Probability)

Outcome probability
Date

3. Market Data

Contract Snapshot

This market resolves YES if the specific candidate associated with the contract wins the Idaho Senate race, and NO if they do not. Resolution is determined by the winning party of the Idaho Senate race. The market opens for trading on November 3, 8:00 AM EST, with a maximum payout date of November 3, 2027.

Available Contracts

Market options and current pricing

Outcome bucket Yes (price) No (price) Last trade probability
Jim Risch $0.97 $0.04 96%
Todd Achilles $0.04 $0.97 4%
David Roth $0.01 $1.00 1%

Market Discussion

As of September 9, 2026, the 2026 U.S. Senate election in Idaho has not yet taken place, with the general election scheduled for November 3, 2026 [1][2]. Incumbent Republican Senator Jim Risch is seeking re-election against multiple candidates, including Independents Todd Achilles and Natalie Fleming, and Libertarian Matt Loesby, after Democratic nominee David Roth withdrew from the race [3][4][5]. Prediction markets and political forecasters heavily favor Senator Risch, with win probabilities for a Republican victory generally assigned between 93-96% [6][7][8][9], and Decision Desk HQ forecasting a 99% probability for Risch as of September 1, 2026 [2], consistently attributing this to Idaho's entrenched Republican advantage [6][7][8][9].

Sources (9)
  1. 1United States Senate election in Idaho, 2026 - Ballotpediaballotpedia.org
  2. 22026 Idaho US Senate Forecastvotes.decisiondeskhq.com
  3. 32026 United States Senate election in Idaho - Wikipediaen.wikipedia.org
  4. 4Risch v. Achilles may be Idaho’s most active US Senate race in years. Here’s where they stand. • Idaho Capital Sunidahocapitalsun.com
  5. 5Idaho US Senate candidate David Roth removes name from general election ballotyahoo.com
  6. 6TO: Interested Parties FROM: Erik Iverson, President, Peak Insights RE: Senator Jim Risch Has Wide Lead in General Election Senate Race A recent statewide survey of likely 2026 general election voters (N=500 live calls; MoE +/-4%; June 6- 7, 2026) shows Senator Jim Risch leading by 40 points over his next closest competitor, Democrat David Roth. On the full-field ballot, Senator Risch also leads by wide margins over both Independent candidates (+48 Risch over Todd Achilles and +50% Risch over Natalie Fleming) and the Libertarian candidate (+53 Risch over Matt Loesby).senatorrisch.com
  7. 7Idaho — U.S. Senate — 2026 forecast — Akashicakashic.app
  8. 8Idaho Senate Election Winner Predictions & Odds 2026 | Polymarketpolymarket.com
  9. 9Which Party will win the 2026 Idaho Senate Election? | Manifoldmanifold.markets

4. Trust Index

Octagon Trust Index Kalshi 83 Good
How it adds up
Integrity80% of score85Strong
Trade quality20% of score76Good

Includes the cost to trade: a $10,000 order loses about 1% of the price to slippage.

Trust score83Good

Weighted blend with hard caps — a critically weak safety pillar, or a severe trading anomaly, caps the total regardless of the rest. Full methodology · About the Trust Index

Trust profile
Integrity4 screens run · 6 don't apply
Market integrity
85Strong

Outcome is hard to influence

No suspicious activity on any screen

Screened clean
Large tradesNo single trade dominates the tape. Clear
Thin-volume movesMoves carried volume Clear
Size patternsTrade sizes look organic. Clear
2 screens not run
Outcome control · doesn't apply to this market type
Thin-leg conviction · doesn't apply to this market type
Info fairness
80Good

Structural prior — no screens apply

No suspicious activity on any screen

Screened clean
Information exposureNo concentrated group can know the outcome materially early. Clear
4 screens not run
Move vs. catalyst · doesn't apply to this market type
Longshot repricing · doesn't apply to this market type
Pre-broadcast certainty · doesn't apply to this market type
Cross-venue timing · doesn't apply to this market type
Resolution quality
92Strong

Resolution mechanism is dependable

No suspicious activity on any screen

Resolution rules read: Clear

Liquidity
77Tradeable

Fills fine at modest size

3 contracts · worst first

David Roth27
Very thin · low confidence

Light recent trading — size may not fill near the screen price.

Todd Achilles41
Thin · low confidence

Light recent trading — size may not fill near the screen price.

Jim Risch86
Deep · medium confidence

Typical bar range 0.3% of price over 6 traded bars

24h traded notional $2,735 · 24h
Move quality
81Confirmed

Moves came with real volume

3 contracts · worst first

Todd Achilles81
Confirmed · high confidence

Volume confirms the move over 6h

Jim Risch—
No significant move (24h)

Price was stable over the last 24 hours.

David Roth—
No significant move (3d)

Price was stable over the last 3 days.

Rule clarity
100Clear

Counts toward Resolution quality, not here

3 contracts · worst first

Jim Risch100
Clear · high confidence

All checks pass

objective outcome · Clearofficial source · Cleartime boundary · Clear
Todd Achilles100
Clear · high confidence

All checks pass

objective outcome · Clearofficial source · Cleartime boundary · Clear
David Roth100
Clear · high confidence

All checks pass

objective outcome · Clearofficial source · Cleartime boundary · Clear
Trade quality
76Good

Order book supports trading

Deep and tight enough to trade efficiently.

Outcome quality 80 (notional-weighted across 3 scored legs)

$100 order: 0.4c slippage (<1% of a 90.6c contract)

$1,000 order: 0.8c slippage (<1% of a 90.6c contract)

$10,000 order: 1.3c slippage (~1% of a 90.6c contract)

Jim Risch86Market scoreLiquidity86Move quality–Rule clarity100
Why 86
Liquidity
86 · Deep · medium confidence

Typical bar range 0.3% of price over 6 traded bars

24h traded notional $2,735 · 24h
Move quality
No significant move (24h)

Price was stable over the last 24 hours.

Rule clarity
100 · Clear · high confidence

All checks pass

objective outcome · Clearofficial source · Cleartime boundary · Clear
Todd Achilles41Market scoreLiquidity41Move quality81Rule clarity100
Why 41
Liquidity
41 · Thin · low confidence

Light recent trading — size may not fill near the screen price.

Move quality
81 · Confirmed · high confidence

Volume confirms the move over 6h

Rule clarity
100 · Clear · high confidence

All checks pass

objective outcome · Clearofficial source · Cleartime boundary · Clear
David Roth27Market scoreLiquidity27Move quality–Rule clarity100
Why 27
Liquidity
27 · Very thin · low confidence

Light recent trading — size may not fill near the screen price.

Move quality
No significant move (3d)

Price was stable over the last 3 days.

Rule clarity
100 · Clear · high confidence

All checks pass

objective outcome · Clearofficial source · Cleartime boundary · Clear

underwriting_v1.4 · computed Sep 26, 2026

5. What do the latest polls and election forecasts indicate for incumbent Jim Risch's lead over Todd Achilles ahead of the November 2026 election?

Jim Risch Win Probability (Decision Desk HQ)99% [1][2]
Jim Risch Win Probability (Prediction Markets)93% to 96% [3][4][5][6]
Idaho Senate Race RatingSafe Republican [4][6]
Incumbent Jim Risch is strongly favored for re-election in Idaho. As of September 2026, Republican Senator Jim Risch is highly likely to win re-election to the U.S. Senate. Decision Desk HQ forecasts a 99% probability of victory for Risch [1][2]. Prediction markets, observed on September 9, 2026, also indicate a high likelihood of his win, assigning him a probability between 93% and 96% [3][4][5][6]. Forecasters consistently rate the Idaho Senate race as Safe Republican due to the state's strong partisan lean, even with unusual activity from the Achilles campaign [4][6].
Recent polls present conflicting views on Risch's lead. Despite the strong forecasts, recent polling data offers contrasting perspectives on Risch's standing against independent candidate Todd Achilles [3][4][5][7][1][2][8]. An August 2026 Bullfinch survey, as well as another conducted by The Bullfinch Group from August 4-7, 2026, showed Todd Achilles leading Risch 38% to 33% [3][4][5][7][1][2][8]. Conversely, a Peak Insights poll from August 11-13, 2026, indicated Risch with a significant lead of 52% to Achilles' 18% [1][2][8]. The general election is scheduled for November 3, 2026, and will include incumbent Jim Risch (R), Todd Achilles (Independent), and David Roth (D) among others [1][2][8].
Sources (8)
  1. 12026 Idaho US Senate Forecastvotes.decisiondeskhq.com
  2. 22026 Idaho US Senate Forecast | DDHQnewsnation-votes.decisiondeskhq.com
  3. 32026 Idaho Senate Polls | Polling Average & Latest Polls - Pollsmaxpollsmax.com
  4. 4Risch v. Achilles may be Idaho's most active US Senate race in...idahocapitalsun.com
  5. 5Republican Idaho Senate Odds Drop 30pp to 67% Despite Risch's 40-Point Poll Lead | Prediction Huntpredictionhunt.com
  6. 62026 Idaho Senate Election: Polls & Odds | Prediction Edgepredictionedge.com
  7. 7[Bullfinch] Idaho Senate Poll: Todd Achilles 38%, Jim Risch 33%reddit.com
  8. 8United States Senate election in Idaho, 2026 - Ballotpediaballotpedia.org

6. How does Jim Risch's 2026 primary performance and general election polling compare to his previous Senate campaigns in Idaho?

2026 Primary Vote67.26% (May 19, 2026 [1][2][3])
Forecasting Model Rating'Solid Republican' or 'Safe Republican' ([4][1][5])
Projected Win Probability (Decision Desk HQ)99% ([6])
Jim Risch easily won the 2026 Republican primary election. He secured the Republican nomination for the 2026 Idaho Senate race on May 19, 2026, receiving 67.26% of the primary vote [1][2][3]. The provided research does not include information on Risch's primary performance in previous Senate campaigns, preventing a direct comparison to his past primary election results.
General election forecasts strongly favor Risch despite conflicting internal polls. For the 2026 general election, initial polling data presents conflicting outcomes; one campaign-internal poll indicates Risch leading by 34 points, while an opponent's poll reports a narrower 4-point margin [7]. Despite these variations, major political forecasting models, including Cook Political Report and Sabato’s Crystal Ball, consistently rate the Idaho Senate race as 'Solid Republican' or 'Safe Republican' [4][1][5]. Prediction markets assign an approximately 93% probability of a Republican victory, and Decision Desk HQ projects Jim Risch as the winner of the 2026 Idaho U.S. Senate general election with a 99% probability [4][1][5][6]. This robust outlook aligns with his historical general election successes, which include securing 57.7% of the vote in 2008, 65.33% in 2014, and 62.62% in 2020 [7][4][1][5][8][9][10][11].
Sources (11)
  1. 1United States Senate election in Idaho, 2026 - Ballotpediaballotpedia.org
  2. 22026 Idaho US Senate | Live Election Resultsvotes.decisiondeskhq.com
  3. 32026 Idaho US Senate Live Election Results | DDHQnewsnation-votes.decisiondeskhq.com
  4. 4ID Senate 2026 - Cook Political Reportcookpolitical.com
  5. 5Idaho Senate Election Winner Predictions & Odds 2026 | Polymarketpolymarket.com
  6. 62026 Idaho US Senate Forecastvotes.decisiondeskhq.com
  7. 7Polls show wildly different outcomes in Idaho US Senate raceidahostatesman.com
  8. 8List of United States Senators from Idaho - Ballotpediaballotpedia.org
  9. 92020 Senatorial General Election Results - Idahouselectionatlas.org
  10. 10United States Senate elections in Idaho, 2014 - Ballotpediaballotpedia.org
  11. 112014 Senatorial General Election Results - Idahouselectionatlas.org

7. Following David Roth's withdrawal, how are Democratic and independent voters expected to align between Jim Risch and Todd Achilles?

David Roth Withdrawal DateJuly 28, 2026 [1][2][3][4][5]
June 2026 Polling (Risch)40% [6]
Risch Predicted Win ProbabilityExceeds 99% (as of September 2026) [7]
David Roth withdrew, aiming to boost independent Todd Achilles' challenge. Democratic nominee David Roth officially withdrew from the 2026 Idaho Senate race on July 28, 2026, with the explicit goal of clearing the path for independent candidate Todd Achilles to contend against incumbent Republican Jim Risch [1][2][3][4][5]. Initial polling conducted in June 2026 indicated some alignment of non-Republican voters behind Achilles, showing Risch at 40% and Achilles at 36% in a direct contest [6].
Jim Risch remains heavily favored despite Achilles' consolidated support. Despite the reported consolidation for Achilles, incumbent Republican Jim Risch is strongly favored by various prediction markets and political forecasts [8][9][4][10]. As of September 2026, Risch's projected win probability frequently exceeds 99% [7]. Polling data for the race has shown considerable inconsistency, with some internal polls from Achilles' campaign indicating he is within 4 points of Risch, while other polls linked to campaigns suggest Risch holds a lead of up to 34 points [8][9].
Sources (10)
  1. 1Democrat David Roth to withdraw from Idaho Senate race, leaving...spokesman.com
  2. 2Idaho US Senate candidate David Roth removes name from general...idahocapitalsun.com
  3. 3Idaho Democrat is latest Senate nominee to drop out in boost to...rollcall.com
  4. 42026 United States Senate election in Idaho - Wikipediaen.wikipedia.org
  5. 5Julian Beaudion becomes the fifth major or minor party U.S. Senate nominee to withdraw from a general election this year - Ballotpedia Newsnews.ballotpedia.org
  6. 6Election 2024 Senate Polls - Dave Leip's Atlas of U.S. Presidential Electionsuselectionatlas.org
  7. 72026 Idaho US Senate Forecastvotes.decisiondeskhq.com
  8. 8Polls show wildly different outcomes in Idaho US Senate raceidahostatesman.com
  9. 9United States Senate election in Idaho, 2026 - Ballotpediaballotpedia.org
  10. 10Idaho's Senate Election - VoteHubvotehub.com

8. How does the campaign fundraising of Jim Risch compare to that of independent challenger Todd Achilles for the 2026 election cycle?

Jim Risch Total Raised$4,431,093 (July 2026 FEC filing) [1][2][3]
Todd Achilles Total Raised$692,245 (July 2026 FEC filing) [4][2][3]
Todd Achilles Cash on Handapproximately $140,788 (as of March 31, 2026) [5]
Incumbent Senator Jim Risch significantly outpaces challenger Todd Achilles in campaign fundraising. For the 2026 election cycle, Senator Risch's campaign fundraising substantially exceeds that of independent challenger Todd Achilles. As of the July 2026 FEC filing, Risch had raised $4,431,093, while Achilles had accumulated $692,245 [1][2][3][4].
Senator Risch has accumulated substantial funds and spent heavily on his campaign. Senator Jim Risch's re-election campaign had amassed $4,431,093 in total fundraising and expended $3,089,996 for the 2026 cycle by the July 2026 FEC filing [1][2][3]. His campaign also reported raising over $3.35 million in total receipts between January 1, 2025, and June 30, 2026, demonstrating consistent financial activity [1][6].
Independent challenger Todd Achilles has raised considerably less than the incumbent. In contrast, independent challenger Todd Achilles' 2026 Idaho Senate campaign had raised $692,245 and spent $506,311 as of the July 2026 FEC filing [4][2][3]. Furthermore, Achilles reported approximately $140,788 in cash on hand as of March 31, 2026, which represented a significant financial disparity when compared to Senator Risch's resources [5].
Sources (6)
  1. 1RISCH, JAMES E MR. - Candidate overview - FECfec.gov
  2. 22026 Idaho US Senate Forecastvotes.decisiondeskhq.com
  3. 32026 Idaho US Senate Forecast | DDHQnewsnation-votes.decisiondeskhq.com
  4. 4ACHILLES, TODD BAKER - Candidate overview | FECfec.gov
  5. 5Idaho Democrat Hits 48% in Senate Market Despite $0 War Chest | Prediction Huntpredictionhunt.com
  6. 6Who Wins Idaho Senate 2026? Republican Odds Fall to 66% | Prediction Huntpredictionhunt.com

9. What is Todd Achilles's political platform and what is his strategy for building a coalition to challenge Jim Risch in a deeply Republican state?

Unaffiliated Voters in IdahoAbout 25% of the electorate [1][2]
Incumbent Probability of Winning (2026)93% or higher (prediction markets) [3][4][5][6]
Decision Desk HQ Forecast99% probability for Jim Risch (Safe Republican, R+28) [7][8]
Independent candidate Todd Achilles prioritizes combating corruption and reforming government processes. An Army veteran, his platform centers on combating congressional corruption, advocating for term limits, and reforming campaign finance [9][10][11]. Key priorities include breaking the two-party "duopoly," reducing national debt, improving donor transparency, enacting antitrust measures, overturning Citizens United, banning congressional stock trading, and ending the revolving door between government and lobbying [9][10][11]. Achilles also highlights his background as an Army veteran, former state legislator, and business executive, supporting responsible land management and local economies [10].
Achilles aims to build a broad coalition, but faces long odds. His strategy involves uniting moderate Republicans, unaffiliated voters, and Democrats to challenge incumbent Jim Risch in Idaho [1][2]. He seeks to appeal to moderate Republicans disenchanted with their party's rightward shift, the approximately 25% of the electorate who are unaffiliated voters, and Democrats looking for an alternative candidate [1][2]. However, as of early September 2026, political forecasters and prediction markets overwhelmingly favor incumbent Republican Jim Risch to win the 2026 U.S. Senate election, with probabilities often exceeding 93% [3][4][5][6]. Decision Desk HQ specifically forecasts Jim Risch with a 99% probability of victory, characterizing the race as Safe Republican with a projected margin of R+28 [7][8].
Sources (11)
  1. 1Risch v. Achilles may be Idaho's most active US Senate race in...idahocapitalsun.com
  2. 2Idaho Senate Republican Odds Fall 31 Points to 66% on Independent Bid | Prediction Huntpredictionhunt.com
  3. 3Polls show wildly different outcomes in Idaho US Senate raceidahostatesman.com
  4. 4Idaho's Senate Election - VoteHubvotehub.com
  5. 5Idaho Senate Election Winner Predictions & Odds 2026 | Polymarketpolymarket.com
  6. 62026 Idaho Senate Election: Polls & Odds | Prediction Edgepredictionedge.com
  7. 72026 Idaho US Senate Forecastvotes.decisiondeskhq.com
  8. 82026 Idaho US Senate Forecast | DDHQnewsnation-votes.decisiondeskhq.com
  9. 9Todd Achilles for Idahoachillesforidaho.com
  10. 10United States Senate election in Idaho, 2026 - Ballotpediaballotpedia.org
  11. 11Todd Achilles – IVA2026 - Independent Veterans of Americaindependentveteransofamerica.org

10. What Could Change the Odds

Key Catalysts

Market probabilities for U.S. Senate control are influenced by several catalysts. These include unexpected polling results in key battleground states, candidate withdrawals, court rulings on ballot access, and major political developments [1][2][3]. Liquidity often increases in prediction markets as the November 3 election date approaches [1][2][3].
While national control of the U.S. Senate in 2026 remains highly competitive in prediction markets, with probabilities fluctuating around a toss-up between Democratic and Republican control as of early September 2026 [4][1][2][3], the Idaho U.S. Senate race shows a different dynamic. As of September 9, 2026, Decision Desk HQ forecasts the Idaho race as "Safe Republican", with incumbent Jim Risch holding a 99% probability of winning the election [5][6]. Consequently, any major political developments or unexpected polling shifts that alter this strong incumbent advantage would constitute key catalysts for the Idaho-specific market [1][2][3]. The general election is scheduled for November 3, 2026 [7][8][9][10][11][5][6].

Key Dates & Catalysts

  • Expiration: November 03, 2027
  • Closes: November 03, 2027
Sources (11)
  1. 1Senate 2026 Odds: Live Prediction Market Tracker for Chamber Control – Bellwetherbellwether.market
  2. 2Party Winning the Senate in 2026 Odds: Democratic Party Leads at 52% | Live Oddspredictioncircle.com
  3. 32026 Live Midterms Forecasts by State | Kalshikalshi.com
  4. 4Which party will win the Senate in 2026? Predictions & Od... | Polymarketpolymarket.com
  5. 52026 U.S. Senate Forecast | Decision Desk HQvotes.decisiondeskhq.com
  6. 62026 Idaho US Senate Forecastvotes.decisiondeskhq.com
  7. 7ID voter guide for the General election on Nov 03, 2026.ivoterguide.com
  8. 82026 Idaho Senate race — polls, candidates & voter guide — IJRijr.com
  9. 92026 Election Calendar: Primary and General Election Dates | AP Newsapnews.com
  10. 10The 2026 Midterms: Key Dates and Events - Bipartisan Policy Centerbipartisanpolicy.org
  11. 11United States Senate election in Idaho, 2026 - Ballotpediaballotpedia.org