Robinhood Expands With MIAXdx, Kalshi Hits ~$11B, and Polymarket Progresses Through U.S. Market Barriers

Deepening Competition Among Robinhood, Kalshi, and Polymarket Signals a Structural Shift in Event-Based Trading

TL;DR

• Robinhood and Susquehanna’s acquisition of MIAXdx (formerly LedgerX under FTX) positions the firm to challenge Kalshi and Polymarket.
• Kalshi’s valuation surge and global volume dominance show accelerating institutional confidence in event-contract markets.
• Polymarket pushes toward U.S. re-entry as regulatory disputes and lawsuits raise volatility across the sector.

Robinhood has moved aggressively into the prediction-markets space after acquiring a 90% stake in MIAXdx — the exchange formerly known as LedgerX during its time under FTX — marking a pivotal expansion meant to bring event-based trading to mainstream retail flows. MIAX paid $50 million for LedgerX during the FTX bankruptcy process in 2023, later retaining a 10% share under the new ownership structure alongside Robinhood and Susquehanna International Group. 

The acquisition builds on a product line launched in March 2025, where Robinhood’s prediction-market offering has already processed more than nine billion contracts for over one million users. Messaging from executives describes the acquisition as a response to “strong customer demand,” with plans to build infrastructure internally while remaining open to additional purchases if conditions align. The company also expects to launch its derivatives and futures exchange through MIAXdx in 2026, with Susquehanna set to act as initial liquidity provider, and internal data suggests Robinhood users account for roughly 25% to 35% of Kalshi’s daily volume. Revenue tied to the firm’s event contracts is reportedly annualizing above $200 million as of September 2025, positioning the platform to collide directly with category leaders.

Kalshi has surged ahead in valuation and activity, drawing global attention after doubling its valuation from approximately $5 billion to nearly $11 billion within weeks, fueled by a roughly $1 billion funding event that followed an earlier $300 million raise backed by Sequoia Capital, Andreessen Horowitz, Coinbase Ventures, and other deep-cap investors. The platform claims users across over 140 countries, a geographical reach that underscores the accelerating shift of event-contract products beyond U.S. borders. 

Weekly prediction-market volume recently climbed to $3.68 billion, more than 2.4× last year’s election peak, driven heavily by Opinion Labs, which now accounts for almost one-third of total volume despite holding only 14% of open interest, a split that reflects reward-farming rather than organic trading. A single Opinion Labs market — “Will Satoshi move any Bitcoin in 2025?” — generated $1.28 billion, or 32% of the platform’s volume alone. 

Category distribution shows Polymarket remains broadly diversified with 38% sports, 28% crypto, and 17% politics across weekly turnover, while Kalshi skews sharply toward sports with 85.5% of its volume tied to athletic outcomes.

Growing volume and rising valuations now sit against a mounting legal backdrop, as Kalshi faces a class-action lawsuit in the Southern District of New York alleging that the platform operates an unlicensed sportsbook while presenting wagers as event contracts. The filing claims Kalshi “dupes consumers into thinking they are legally gambling against other consumers, when they are actually gambling against the house,” arguing that since January 2025 the company has offered sports bets — point spreads, overs/unders, player props, and same-game parlays — even in jurisdictions where online betting is prohibited. 

Plaintiffs point to Kalshi ads urging users to “Bet on the NFL” and describing access as “Legal in 50 states,” while noting that 90% of Kalshi’s September 2025 volume derived from sports, with gamblers placing more than $2 billion during that period. Regulators have issued cease-and-desist orders, yet the suit claims Kalshi continues to operate nationwide and plaintiffs are now seeking restitution, fees, and damages.

Polymarket, long constrained by U.S. restrictions, is charting its way back into the domestic market through the acquisition of a regulated exchange and clearinghouse (QCEX), a blueprint that mirrors Robinhood’s MIAXdx pathway and signals that non-regulated positioning may no longer sustain competitive growth. Legal exposure remains a critical variable, however, as regulators continue to classify certain contracts — particularly sports-linked outcomes — as potential unlicensed wagering. This creates a climate where growth, user acquisition, and valuation sit alongside unresolved policy interpretation, forming what analysts describe as a “bet on regulation.” 

The accelerating rise of Kalshi and the entrance of Robinhood through a former FTX-linked exchange highlight a shifting battleground that merges fintech structure with betting-style behavior, while Polymarket’s re-entry effort underscores the strategic pressure to secure U.S. compliance if long-term scale is to be realized. The three-way rivalry now defines a sector where political outcomes, macroeconomic releases, earnings reports, and real-world events trade like futures — a market whose expansion depends as much on appetite as on legal oxygen.

This article has been refined and enhanced by ChatGPT.