Prediction market trading raises manipulation concerns in Los Angeles election betting

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Highlights

Over $47 million was traded across Kalshi, Polymarket U.S., and Polymarket International in the 2026 Los Angeles mayoral primary, the most heavily traded mayoral contest to date.
On May 20, a single trader spent $1.25 million on Pratt-related contracts on Kalshi, causing a price spike from 29 to 45 cents before rapid correction.
Wagering on 2026 congressional election contracts already more than tripled 2024 levels, intensifying concerns about manipulation and misleading signals in expanding prediction markets.

Trading patterns and platform monitoring

As first reported by CNBC, the mismatch between prediction market prices and the June Los Angeles mayoral primary result is drawing attention to whether trading can temporarily inflate a candidate's apparent support. The outlet's reporting says the race attracted more than $47 million in trades across Kalshi, Polymarket U.S. and Polymarket International, making it the most heavily traded mayoral contest of 2026.

On the eve of the primary, one market gave Pratt a 78% chance of advancing to the November runoff, despite his limited political background and lack of prior elected office. After the Palisades fire destroyed his home, he turned criticism of the city's response into a campaign message that helped attract speculative interest on the platforms.

Kalshi says it detected and reported price spikes in trading on the race in a case study published in July. The company says that on May 20, a trader spent $1.25 million on "Yes" contracts tied to Pratt becoming Los Angeles' next mayor, and one trade pushed the price from 29 cents to 45 cents before it reverted within nine seconds as the market self-corrected.

Election impact and wider market growth

Pratt ultimately finished third, but his supporters used the failed market signal to cast doubt on the integrity of the election. Dean Logan, registrar-recorder for the Los Angeles County Clerk's Office, says in a statement to CNBC that prediction markets can deepen confusion when people treat projections as more authoritative than actual vote counting.

That concern is becoming more significant as election wagering expands. According to ACDC, the amount wagered on contracts related to the 2026 congressional elections has already more than tripled bets on the 2024 races, while Kalshi says viewers of its midterm election markets outnumber active traders by 5-to-1.

Kalshi says its election markets have often been accurate, writing that since 2024, candidates favored by its U.S. election markets have gone on to win roughly nine times out of 10. But an analysis for CNBC by the Anti-Corruption Data Collective says there are numerous price spikes across Kalshi and Polymarket International during the Los Angeles mayoral race that push odds in Pratt's favor, reinforcing the view that liquid political contracts can still create misleading impressions even when markets later correct.

In our earlier article on the Ibovespa’s post-election selloff, we covered how President Luiz Inácio Lula da Silva’s re-election triggered a sharp risk-off move and heightened volatility across major Brazilian sectors. We also noted that bearish technical signals and policy uncertainty kept the index under sustained downside pressure, leaving it vulnerable to further declines despite periodic bounce scenarios flagged by analysts.

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