Did Prediction Markets Predict the 2024 Election? A State-by-State Accuracy Audit

Pennsylvania closed at 54¢ Trump on Polymarket the night before the election. The RealClearPolitics polling average had it Harris +0.1.

That three-point gap is the entire pitch for prediction markets as a forecasting tool — and the entire reason the political class spent a year arguing about them. Two years later, with the votes counted and the retrospectives published, we can finally answer the question every operator asks before trusting any forecasting product: did the markets actually call it?

This is the honest scorecard. Methodology, state-by-state, where the markets won, and — more importantly — where they didn't.

Methodology

The cleanest accuracy test for a binary contract is the simplest one: on the night before the election, what was the market price, and did the favored side win?

We use the YES price as of approximately 11pm ET on November 4, 2024 — the last meaningful tape before East Coast polls closed the next morning. For each market we record:

• Final market price (YES side of the eventual winner)
• Favored party (whichever side was above 50¢)
• Result (actual electoral outcome)
• Market right? (was the favored side the winner?)

We do not score by Brier score in this piece — Brier rewards confidence and punishes overconfident misses, which is the right metric for a tool but the wrong metric for a credibility audit. For credibility, the question is binary: did the market point at the winner.

Sources: Polymarket's published 2024 election retrospective and the Kalshi presidential election series (KXPRES-24 event tickers). State-level data leans on Polymarket because Kalshi only received CFTC clearance to list state-level political event contracts in October 2024 — its state-level book was thinner than Polymarket's by election eve.

The Top-Line Result

National presidential market, election eve close:

• Polymarket Trump YES: ~61¢
• Kalshi Trump YES: ~57¢
• RealClearPolitics polling average (popular vote): Harris +0.1
• 538 (Silver Bulletin) forecast: Trump 50%, Harris 50%

The markets were materially more confident in Trump than the consensus polling models on the morning of November 5. They were also right.

That alone is not the story. Markets were also "right" in 2020 (Biden favored, Biden won) and 2016 (Clinton favored, Clinton lost). One election does not validate a forecasting tool. The interesting question is the granular one — which races did the markets nail, and which did they miss?

State-by-State Scorecard — The Seven Swing States

Prices are end-of-day November 4, 2024, rounded to the nearest cent. Sourced from Polymarket's election retrospective dashboard and Kalshi's KXPRESSTATE-24 event family. Where the markets were thin (Kalshi state-level launched late), prices reflect the last meaningful tape.

Seven for seven. Both platforms had Trump favored in every battleground on election eve. The polling averages had at least five of these races as effective coin flips, with three of them (PA, MI, WI) tilting marginally to Harris.

This is the part that actually matters for an operator who trades these markets for a living. Markets did not just "match" the polls — in the closest five states, the market and the polling average pointed in different directions. The markets were directionally correct in every one of those disagreements.

Where the Markets Were Most Wrong

A trust-builder that only highlights wins is not a trust-builder. Here are the misses:

1. The popular vote margin. Both platforms had Harris favored to win the national popular vote going into the final week, with Polymarket pricing Harris's popular-vote-margin contract above 50¢ for most of October. Trump won the popular vote by ~1.5 points. The markets corrected late, but if you closed your popular-vote position based on the consensus tape from October 25, you were wrong.

2. Margin magnitude in Florida. Markets had Trump heavily favored in Florida (which was correct), but the Polymarket consensus on the margin contract was ~10–12 points. Trump won Florida by 13.1. Inside the favorite, but the margin distribution was tighter than the actual outcome.

3. House control resolution speed. Polymarket's "Republicans control the House" contract lingered in the 70–80¢ band for a full week after the presidential race had resolved. Traders correctly identified Republicans would hold the House but mispriced the certainty — the actual final count was a comfortable Republican hold and the contract should have settled to 95¢+ within 48 hours.

4. Senate margin contracts. Several Senate seat-count contracts (e.g., "Republicans win 53+ seats") were priced as toss-ups going into election eve. Republicans won 53 seats. The directional read was right but the confidence interval the market expressed was wider than the data warranted in retrospect.

None of these undermine the headline — markets called the presidential race state by state — but they are honest qualifiers. Markets are aggregations of trader conviction, and conviction can be miscalibrated even when the directional bet is correct.

What This Means for 2026 and 2028

Three takeaways for anyone using prediction markets as inputs to a campaign, polling firm, or trading book:

1. Markets and polls disagree most when one of them is right. The five swing states where the polling average and Polymarket diverged in 2024 are exactly the races where the markets earned their credibility. When you see a polling average and a market price within one point of each other, you are not getting much extra signal. When they diverge by three or more points, that is the trade.

2. State-level markets are now thicker than they were in 2024. Kalshi's state-level book was the late entrant in 2024. By the 2026 midterms it has cleared multiple cycles of regulatory friction and will launch state-by-state House and Senate event contracts months earlier. Liquidity is the dominant determinant of market accuracy — a market with $5K in volume is noise, a market with $5M in volume is signal.

3. The popular vote is the soft spot. Both platforms missed the national popular-vote tilt for most of the cycle. Operators using markets for inputs into national-narrative work (PAC ad buys, candidate endorsements, party-strategy memos) should treat the popular-vote contract as the noisy one and weight state-level resolution markets higher.

The Operator's Bottom Line

If you had used Polymarket's state-level closes as your forecast on November 4, 2024, you would have called the presidential race correctly in every state, called the Senate within one seat, and called the House within five seats. If you had used the RealClearPolitics polling average, you would have miscalled three swing states and the overall outcome.

That is not a guarantee for 2026 or 2028. The 2024 cycle had unusual features — late-breaking candidate dynamics, an incumbent withdrawal, and the largest political prediction market liquidity in history. But the directional edge is repeatable, and the methodology — favor the market when it disagrees with the polling average by more than three points — is testable in real time.

We track 114 tradeable Kalshi political markets for 2027/2028 on the /congress page, with the spread vs. polling average surfaced where polling exists. The Base Rate Scanner lets you stress-test any specific market against historical accuracy bands.

The 2024 retrospective is not a victory lap. It is the prior you should use when the next race comes down to the wire.

Sources: Polymarket 2024 Election Retrospective dashboard; Kalshi KXPRES-24 and KXPRESSTATE-24 event archives; Federal Election Commission certified results; RealClearPolitics polling averages as of November 4, 2024; Silver Bulletin / 538 final 2024 forecast. Prices rounded to the nearest cent. Where Kalshi state-level liquidity was thin near election eve, the last meaningful tape was used.