Tools chosen: kalshi_direct kalshi_related polymarket_related claude_news wikipedia code_execution fred

Sub-questions (Fermi decomposition)

Planner reasoning

This is a long-horizon Kalshi market on a Democratic trifecta in the 2028 US elections; the primary anchor is the Kalshi price itself, cross-checked against Polymarket's 2028 presidential/Congress markets. Key drivers are the conditional structure (presidential win probability × correlated House/Senate outcomes) and especially the 2028 Senate map, which is structurally hard for Democrats. Research should gather current prices for each component and structural facts about the 2028 Senate class.

# Current state Kalshi's "Democratic Sweep" contract (POWER-28-DH-DS-DP) prices Yes at 55%, up sharply (+7pts) over 30 days but flat/slightly down (-1pt) over 7 days. This sits well above model-based estimates (~19-41%) built from historical trifecta base rates and the 2028 Senate map, suggesting the market may be pricing strong current Democratic momentum (2026 midterm environment, high Dem presidential odds) more than structural Senate-map friction. # Timeline of key events - 2024-11: Republicans won the presidency (Trump) and Senate, retained House — established the current unified GOP government baseline (Wikipedia, confirmed). - 2025 (ongoing): Trump serving nonconsecutive second term; ineligible for 2028 re-election under 22nd Amendment (confirmed, structural). - Early 2026: Democratic 2028 presidential win probability on prediction markets ~54% (reported, Newsweek). - 2026 (through Aug): 58 House members (24 D, 36 R) announce retirement — second-most in US history (Wikipedia, confirmed) — signals GOP-heavy attrition ahead of 2026 midterms. - 2026-07/08: Generic ballot averages show Democrats +6 to +8.1 (DDHQ, Nate Silver — reported); unemployment ticking up to 4.1% (FRED, confirmed). - 2026 (as of research date): Democratic 2028 presidential odds risen to ~60-61% on Polymarket per aggregator reporting (reported, not independently verified via Polymarket tool — 0 direct matches found). - Ongoing: Kalshi Democratic Sweep contract has risen from ~39% floor to current 55% over the observed 78-day window (confirmed, Kalshi direct). - 2026-11 (future, not yet occurred): Midterm elections — DDHQ model projects House flipping to Dems (224-211) but Senate remaining 50-50 GOP-controlled via VP tiebreak (reported/projected, not resolved). - 2028-11-07 (future): Presidential, House, and full Senate Class 3 elections — the event this market resolves on. # Event Will Democrats simultaneously win the Presidency, House, and Senate in the 2028 election ("Democratic Sweep")? # Outcomes to forecast Yes / No (binary) # Kalshi market anchor Current YES price: **55%**. 7-day change: -1pt; 30-day change: +7pt. Price range over 78 data points: 39%-60%. Average daily volume: 525 contracts (moderately liquid, most active related-market volume among the cluster). # Sub-question answers 1. **Current Kalshi price / 90-day trend**: 55% currently; trended up from a 39% low to a 60% high over ~78 days, netting +7pts in the last 30 days despite a slight -1pt pullback in the last week (Kalshi direct). 2. **Standalone 2028 market prices**: Kalshi — Dem House control (CONTROLH-2028-D) 72%; Dem Senate control (CONTROLS-2028-D) 56%; Republican presidential party (KXPRESPARTY-2028-R) 41% (implying Dem ≈59%). No standalone Kalshi Dem-president contract was returned directly, but Newsweek reports Polymarket Dem presidential contracts at ~60-61% vs GOP ~38-39%; Polymarket-direct tool found zero matching active 2028 markets (polymarket_related). 3. **2028 Senate seats up / structural floor-ceiling**: Correcting the sub-question's premise — 2028 is **Class 3**, not Class I (Wikipedia, confirmed): 34 seats, currently 19R/15D. Four Dem-held seats (GA, PA, AZ, NV per Newsweek reporting) sit in Trump-won states and are top GOP targets; a separate list (code_execution model) cites GA, MI, MN, NH, VA as exposed — sources disagree on exact list, but consensus is a handful of exposed Dem seats with GA the common thread. Historically this class was stable (net one-seat flip in 2022) (Ballotpedia). 4. **Historical trifecta base rate**: 7/12 elections since 1980 produced a unified trifecta (58.3%), though 2 of those 7 involved 50-50 Senates decided by VP tiebreak (code_execution). Conditional on a Democratic presidential win (n=5), P(Senate D)=80%, P(House D)=60%, joint observed P(both D)=60% — 1.25x the independence-implied rate, indicating real coattail correlation (code_execution). 5. **Current partisan environment**: Generic ballot favors Democrats D+6 to D+8.1 (DDHQ, Nate Silver, reported); unemployment 4.1% (Jul 2026, FRED, confirmed) and CPI rising modestly; Fed funds rate steady at 3.63% (FRED, confirmed). 2026 midterm forecasts (DDHQ) project a Dem House flip (224-211) but GOP retaining Senate 50-50 via tiebreak (reported). 6. **Presidential/congressional correlation**: Historical data shows above-independence joint correlation (1.25x multiplier) between House and Senate outcomes conditional on presidential party win, consistent with declining ticket-splitting; code_execution model adjusts P(House&Senate D | Pres D) to ~41% after applying this multiplier with a map-adjusted Senate probability of 55%. # Key facts (high-confidence, factual) 1. [Wikipedia] 2028 Senate election involves Class 3 seats (19R/15D), last contested 2022. 2. [Wikipedia] Trump is term-limited; 2028 has no incumbent on either ticket. 3. [Kalshi] Sweep contract =55%; Dem House control=72%; Dem Senate control=56%. 4. [FRED] Unemployment 4.1% (Jul 2026), gradually rising from 2025 lows. 5. [code_execution] Historical unified trifecta base rate 1980-2024 = 58.3% (7/12). # Cross-market signals - Kalshi related: Dem House (72%) × Dem Senate (56%) implied independence product ≈40%, vs sweep price of 55% — market pricing meaningful positive correlation/coattails, consistent with historical pattern. - Kalshi presidential proxy: GOP party win 41% → implied Dem ≈59%, roughly consistent with the 55% sweep price if House/Senate are highly correlated with presidency. - Polymarket: No standalone 2028 party-control markets found directly; secondary reporting cites Dem presidential ~60-61%, GOP ~38-39%, up from 54% in Jan. - Sportsbook implied: none available. # Analyst opinions and speculation - Newsweek: Democratic 2028 presidential odds "soaring," momentum widening since January. - DDHQ/Silver Bulletin: 2026 generic ballot environment resembles a 2018-style wave, projecting 25-40 House seat gains for Dems but Senate remaining GOP-controlled. - code_execution model: cautions Kalshi's 55% may be overpricing sweep odds by underweighting Senate-map friction, estimating fair value closer to 19-41% depending on assumptions. - Newsweek caveat: long-dated political prediction-market prices are speculative and shouldn't be treated as firm forecasts. # Directional lean per outcome - **Yes (sweep)**: Favorable generic ballot, rising Dem presidential odds, historical coattail correlation, and Kalshi's own upward 30-day trend all support Yes; but 2028 Senate map still has real GOP-leaning exposure (GA and others) and presidential race remains genuinely contested per multiple sources. - **No (no sweep)**: Structural Senate math (need net gain to secure majority, contested seats in swing states), historical rate of ~41-58% (not near-certainty) for trifecta, and 2026 midterm Senate forecast staying GOP-controlled even with House flip — all argue for meaningful No probability; model-based estimate (19-41%) is notably below Kalshi's 55%. # Gaps / unknowns - No confirmed standalone Polymarket 2028 sweep/party-control market data (tool returned zero matches); reliance on secondary reporting only. - Conflicting lists of "exposed" Democratic Senate seats across sources. - Unclear how much of the +7pt 30-day Kalshi move is driven by 2026 midterm polling vs actual 2028 fundamentals. - Democratic presidential primary field remains fragmented (AOC ~13-18%, Ossoff ~16%, Newsom ~16%), adding uncertainty to the "Dem presidential win" leg. # Calibration anchors - Kalshi current YES price: **55%** (primary anchor). - Model-implied fair value range: ~19-41% (code_execution, historical base rates + map adjustments). - Historical unified trifecta base rate (1980-2024): 58.3% (7/12), or ~50% excluding tiebreak-decided Senates. - Implied cross-market check: Dem House (72%) × Dem Senate (56%) ≈ 40% independence baseline vs 55% sweep price — implies market assumes strong correlation, in line with historical coattail effect (~1.25x observed multiplier).

1. Both forecasters cite Dem Senate control at 56% as "a hard mathematical ceiling" for the sweep, but only Forecast 1 explicitly notes this constraint—neither actually enforces it in their final number (both land at 43-45%, comfortably below 56%, so the ceiling logic is technically respected, but neither explains why they land so close together despite different weighting of the 19-41% model range vs. the 55% market anchor). 2. Both forecasters essentially converge to nearly identical numbers (43% vs 45%) via similar reasoning chains, giving false appearance of independent confirmation; neither explores why the Kalshi price sits so far above their model consensus (55% vs their ~43-45% estimates) — is the market simply wrong, or are they missing information the market has priced (e.g., specific 2028 recruitment/polling data not in the brief)? 3. Neither forecast addresses the "Gaps/unknowns" section's point about the fragmented Democratic primary field (AOC ~13-18%, Ossoff ~16%, Newsom ~16%) — a fragmented primary could depress the eventual nominee's general-election odds relative to the current aggregate "Dem presidential" market price, which neither forecast discounts for. 4. Both forecasters treat the 1.25x historical coattail multiplier as reliable, but the brief notes it's based on only n=5 historical elections with Dem presidential wins since 1980 — a very small sample that neither forecast flags as a source of significant model uncertainty in the 19-41% range itself. 5. Neither forecast grapples with the discrepancy between "conflicting lists of exposed Democratic Senate seats across sources" (GA/PA/AZ/NV vs GA/MI/MN/NH/VA) — this uncertainty about the actual Senate map friction should widen their confidence intervals rather than letting them settle on point estimates near 43-45%. 6. Both forecasters discount the market price toward the model range but neither seriously entertains that the code_execution model's 19-41% might be the outlier (e.g., failing to account for anti-incumbent/wave dynamics not captured in static base rates), which would argue for weighting the market's real-time information more heavily rather than converging toward the model's lower band.

46% (46% confidence)

Yes: 46% No: 54%

The decisive structural fact is that Democratic Senate control is a hard mathematical ceiling on a sweep, and Kalshi's own Senate contract sits at 56% — meaning the 55% sweep price implies a near-certain (~98%) conditional probability of also taking the House and presidency given a Senate win, which is implausible even with strong coattails. A more coherent reconstruction is Senate 56% × P(House & Presidency | Senate D) of roughly 0.75-0.85, yielding ~42-48%; the pure independence product (~24%) and the historical 1.25x coattail multiplier bracket a similar range. I discount the code_execution model's low band (19%) because it leans on static base rates from a tiny sample (n=5 Dem presidential wins) and understates the real-time wave environment — D+6 to D+8 generic ballot, record GOP retirements, and a projected 2026 House flip — that the market is pricing. Offsetting factors keeping this below the market anchor: the Class 3 map exposes several Dem-held seats in Trump-won states (GA in every source list), the fragmented Dem primary field adds nominee risk, and the contract is thinly traded with a ~2.5-year horizon. I therefore land at 46% — just above the two forecasters' 43-45% consensus in deference to the market's information advantage, but below the 55% anchor because of the cross-market inconsistency.

Total pipeline time: 163.9s