{
  "schemaVersion": "vultax-public-research-data-v1",
  "articleUrl": "https://vultax.com/research/polymarket-vs-kalshi-midterms-odds-2026",
  "datasets": [
    {
      "title": "Senate control: the price of a Democratic majority on each venue",
      "columns": [
        {
          "name": "Category",
          "unit": null
        },
        {
          "name": "Polymarket",
          "unit": "¢"
        },
        {
          "name": "Kalshi",
          "unit": "¢"
        }
      ],
      "rows": [
        [
          "Jun 29",
          42.5,
          41
        ],
        [
          "Jun 30",
          41.5,
          42
        ],
        [
          "Jul 1",
          41.5,
          41
        ],
        [
          "Jul 2",
          41.5,
          41
        ],
        [
          "Jul 3",
          44.5,
          40
        ],
        [
          "Jul 4",
          44.5,
          41
        ],
        [
          "Jul 5",
          44.5,
          40
        ],
        [
          "Jul 6",
          44.5,
          40
        ],
        [
          "Jul 7",
          45.5,
          42
        ],
        [
          "Jul 8",
          45.5,
          42
        ],
        [
          "Jul 9",
          46.5,
          44
        ],
        [
          "Jul 10",
          46.5,
          43
        ],
        [
          "Jul 11",
          45.5,
          43
        ],
        [
          "Jul 12",
          46.5,
          43
        ],
        [
          "Jul 13",
          45.5,
          44
        ],
        [
          "Jul 14",
          45.5,
          44
        ],
        [
          "Jul 15",
          45.5,
          46
        ],
        [
          "Jul 16",
          45.5,
          45
        ],
        [
          "Jul 17",
          45.5,
          45
        ],
        [
          "Jul 18",
          44.5,
          43
        ],
        [
          "Jul 19",
          43.5,
          44
        ],
        [
          "Jul 20",
          43.5,
          45
        ],
        [
          "Jul 21",
          43.5,
          44
        ],
        [
          "Jul 22",
          43.5,
          44
        ],
        [
          "Jul 23",
          43.5,
          44
        ],
        [
          "Jul 24",
          43.5,
          44
        ],
        [
          "Jul 25",
          43.5,
          44
        ],
        [
          "Jul 26",
          43.5,
          45
        ],
        [
          "Jul 27",
          43.5,
          45
        ],
        [
          "Jul 28",
          43.5,
          44
        ],
        [
          "Jul 30",
          43.5,
          45
        ],
        [
          "Jul 31",
          43.5,
          46
        ],
        [
          "Aug 1",
          43.5,
          47
        ],
        [
          "Aug 2",
          44.5,
          46
        ],
        [
          "Aug 3",
          44.5,
          46
        ],
        [
          "Aug 4",
          44.5,
          47
        ],
        [
          "Aug 5",
          44.5,
          47
        ],
        [
          "Aug 6",
          44.5,
          44
        ],
        [
          "Aug 7",
          45.5,
          47
        ],
        [
          "Aug 8",
          45.5,
          46
        ],
        [
          "Aug 9",
          45.5,
          46
        ],
        [
          "Aug 10",
          45.5,
          46
        ],
        [
          "Aug 11",
          46.5,
          46
        ],
        [
          "Aug 12",
          50.5,
          49
        ],
        [
          "Aug 13",
          52.5,
          49
        ],
        [
          "Aug 14",
          52.5,
          50
        ],
        [
          "Aug 15",
          52.5,
          48
        ],
        [
          "Aug 16",
          52.5,
          49
        ],
        [
          "Aug 17",
          52.5,
          48
        ],
        [
          "Aug 18",
          50.5,
          49
        ],
        [
          "Aug 19",
          51.5,
          48
        ],
        [
          "Aug 20",
          50.5,
          46
        ],
        [
          "Aug 21",
          50.5,
          46
        ],
        [
          "Aug 22",
          50.5,
          47
        ],
        [
          "Aug 23",
          50.5,
          46
        ],
        [
          "Aug 24",
          49.5,
          46
        ],
        [
          "Aug 25",
          49.5,
          46
        ],
        [
          "Aug 26",
          49.5,
          48
        ],
        [
          "Aug 27",
          50.5,
          49
        ],
        [
          "Aug 28",
          50.5,
          48
        ],
        [
          "Aug 29",
          50.5,
          48
        ],
        [
          "Aug 30",
          50.5,
          48
        ],
        [
          "Aug 31",
          50.5,
          48
        ],
        [
          "Sep 1",
          50.5,
          49
        ],
        [
          "Sep 2",
          50.5,
          48
        ],
        [
          "Sep 3",
          51.5,
          48
        ],
        [
          "Sep 4",
          51.5,
          48
        ],
        [
          "Sep 5",
          51.5,
          48
        ],
        [
          "Sep 6",
          51.5,
          47
        ],
        [
          "Sep 7",
          51.5,
          48
        ],
        [
          "Sep 8",
          51.5,
          47
        ],
        [
          "Sep 9",
          52.5,
          48
        ],
        [
          "Sep 10",
          52.5,
          47
        ],
        [
          "Sep 11",
          52.5,
          48
        ],
        [
          "Sep 12",
          52.5,
          49
        ]
      ],
      "measurementContext": "Daily price in cents, 29 Jun to 12 Sep 2026. Polymarket daily price; Kalshi daily close.",
      "sources": [
        {
          "label": "Kalshi public trade API — events and markets",
          "url": "https://api.elections.kalshi.com/trade-api/v2/events?series_ticker=CONTROLS&with_nested_markets=true",
          "note": "Quotes, open interest and rule text read 18:52 UTC, 12 September 2026; order books every 30 minutes, 12–13 September 2026"
        },
        {
          "label": "Kalshi public trade API — daily candlesticks",
          "url": "https://api.elections.kalshi.com/trade-api/v2/series/CONTROLS/markets/CONTROLS-2026-D/candlesticks?period_interval=1440",
          "note": "Daily closes used for the gap history"
        },
        {
          "label": "Polymarket — Which party will win the Senate in 2026?",
          "url": "https://gamma-api.polymarket.com/events/slug/which-party-will-win-the-senate-in-2026",
          "note": "Quotes and full resolution rules, read 18:53 UTC, 12 September 2026"
        },
        {
          "label": "Polymarket CLOB — price history",
          "url": "https://clob.polymarket.com/prices-history?market=113287701564209339913693347405685749986285999146352375265161592243948562084773&interval=max&fidelity=1440",
          "note": "Daily price points used for the gap history"
        },
        {
          "label": "Polymarket CLOB — order books",
          "url": "https://clob.polymarket.com/books",
          "note": "Midterm contract books, 12–13 September 2026"
        },
        {
          "label": "Polymarket — trading fees",
          "url": "https://docs.polymarket.com/trading/fees",
          "note": "Politics rate 0.04; makers pay nothing; read 2026-09-12"
        },
        {
          "label": "Kalshi — fee rounding",
          "url": "https://docs.kalshi.com/getting_started/fee_rounding",
          "note": "Trade fees are rounded up per fill"
        },
        {
          "label": "OddsShopper — Kalshi fees",
          "url": "https://www.oddsshopper.com/articles/prediction-markets/kalshi-fees",
          "note": "Third-party statement of the 0.07 taker coefficient; Kalshi's own schedule could not be retrieved"
        },
        {
          "label": "Vultax: Kalshi vs Polymarket",
          "url": "https://vultax.com/research/kalshi-polymarket-open-interest-by-category",
          "note": "The venues compared: structure, fees and open interest"
        },
        {
          "label": "Vultax: Kalshi–Polymarket arbitrage after fees",
          "url": "https://vultax.com/research/kalshi-polymarket-arbitrage-gaps-after-fees",
          "note": "How often a midterm gap cleared both venues' fees, and what it returned"
        },
        {
          "label": "Vultax: Is Polymarket legal in the US?",
          "url": "https://vultax.com/research/is-polymarket-legal-in-the-us-2026",
          "note": "Which Polymarket U.S. residents can use"
        }
      ],
      "measurement": {
        "kind": "observed",
        "temporalCoverage": "2026-06-29/2026-09-12",
        "population": "Polymarket \"Which party will win the Senate in 2026?\" Democratic Party market and Kalshi CONTROLS-2026-D",
        "methodology": "Polymarket CLOB daily price history and Kalshi daily candlestick close, aligned by UTC date; 29 July missing from Kalshi's series."
      },
      "id": "direction-chart",
      "kind": "published-chart",
      "description": "Vultax matched 65 midterm contracts across Polymarket and Kalshi. The venues usually sit 1 to 3 points apart, Polymarket prices Democrats higher in 15 of the 18 most-traded outcomes, and $50,000 on a Democratic Senate cost 1.0¢ above the price on Kalshi and 2.4¢ on Polymarket.",
      "articleUrl": "https://vultax.com/research/polymarket-vs-kalshi-midterms-odds-2026",
      "sectionUrl": "https://vultax.com/research/polymarket-vs-kalshi-midterms-odds-2026#direction",
      "publishedAt": "2026-09-16",
      "modifiedAt": "2026-09-16",
      "version": "85dffe44ae6231e8f298bc0887f9840b1667ff3900e8694d0b45db8c44fa7cd7",
      "isLive": false,
      "limitations": "Published research snapshots and calculations; these exports do not contain current quotes or live account data. Observation windows and populations are stated in the source captions and methodology. Missing metadata is unknown, not zero. Prices and order books were read from public venue data on 12 and 13 September 2026 and change continuously. Gap histories compare daily prices taken at different times of day. Price-impact figures exclude fees and assume no reaction from other traders. Not a forecast, a recommendation to trade, or financial advice.",
      "downloads": {
        "json": "https://vultax.com/research/polymarket-vs-kalshi-midterms-odds-2026/data.json?dataset=direction-chart",
        "csv": "https://vultax.com/research/polymarket-vs-kalshi-midterms-odds-2026/data.csv?dataset=direction-chart"
      }
    }
  ]
}