By: David Yaffe-Bellany, William K. Rashbaum, The New York Times
Compiled by: Luffy, Foresight News
On a morning in November 2024, Shayne Coplan, founder of Polymarket, awoke to find uninvited guests in his home. Several FBI agents, wielding a battering ram, stormed into his New York apartment, searching for evidence related to illegal gambling on his platform.
Coplan publicly stated on social media that the raid was a politically motivated crackdown by the Biden administration. But privately, he and his team's advisors harbored a different suspicion, blaming a series of troubles faced by Polymarket on its biggest competitor: Tarek Mansour, CEO of the prediction market platform Kalshi.
Four people familiar with the matter revealed that months before the FBI raid, lawyers from Kalshi visited the Manhattan U.S. Attorney's Office to report issues with Polymarket, a fact never previously disclosed. The lawyers reportedly detailed Polymarket's operational model to prosecutors, focusing on a key problem: the platform should be inaccessible to users in the U.S., but they could still use it normally.
This confrontation was just an extreme eruption of the long-standing animosity between Kalshi and Polymarket. The two are among the hottest startups in the tech industry. While clashes of ambition among Silicon Valley founders are not uncommon, and ego-driven industry feuds are everywhere—like Uber and Lyft battling for the ride-hailing market, or the public sparring between OpenAI's Sam Altman and Anthropic's Dario Amodei—the rivalry between the 28-year-old Coplan and the 30-year-old Mansour has long crossed the boundaries of normal business competition.
More than forty people close to both companies, speaking anonymously, indicated that both men are newly-minted billionaires, determined to monopolize the prediction betting market covering sports, politics, entertainment, and more. Their mutual loathing has permeated almost all business interactions between the two companies.
Shayne Coplan, Polymarket Founder
Dustin Gouker, who writes a long-running column on the prediction market industry, said, "The bad blood runs deep, and the fight has long been personal."
This feud has spread to internal meetings, U.S. congressional hearings, influenced Washington regulatory policy, and triggered unprecedented industry attention and regulatory concerns. The two companies have engaged in trademark disputes, competed for the same business deals, poached each other's talent, traded public accusations in the media, and launched direct personal attacks on social platforms. Both have also established business relationships with Donald Trump Jr., a common public relations strategy in Washington circles during the Trump administration.
Former Kalshi employee and prediction market fund manager Noah Zingler-Sternig commented, "The two companies have crossed the line on many things, making it hard for the public to take either platform seriously."
The hostility is not just about market share; a deeper divide lies in their approaches to business ethics and red lines. Kalshi projects an image of regulatory compliance, insisting on obtaining U.S. regulatory approval before operating domestically. Polymarket, without a domestic license, has long operated its core platform offshore. Kalshi enforces strict identity verification rules and blocks sensitive betting categories; Polymarket users can register without submitting personal information and can even bet on events like the timing of Israeli missile strikes.
While Coplan and Mansour have met over the years, they now almost never communicate, preferring to disparage each other from afar. Mansour, an MIT graduate who calls himself a math enthusiast, once likened their competition to the healthy rivalry between legendary quarterbacks Tom Brady and Eli Manning. Recently, however, he called Polymarket's operational model "illegal and unethical," noting its offshore platform is operated by a Panamanian entity.
In April of this year, Mansour said publicly at an industry conference in Washington, "I don't know what regulations Panama has regarding insider trading in prediction markets—probably none at all."
Coplan, a New York University dropout skilled at sales pitches, rarely mentions Kalshi publicly. But two people familiar with the matter say he privately calls Kalshi a mere copycat of Polymarket's model and believes Mansour has been trying to sabotage him. Coplan is convinced his platform is the industry's best solution, stating on "60 Minutes" last year, "This is the most accurate information tool humanity currently has."
Kalshi spokesperson Elisabeth Diana stated the company learned about the FBI raid through news reports. She added that Kalshi regularly communicates with regulators about compliance and has publicly pointed out that "some companies are harming users and tarnishing the industry's reputation."
Tarek Mansour, Kalshi Co-founder
Diana said, "Tarek has no personal animus toward Shayne. His sole frustration is that Kalshi has spent years pushing for industry compliance, while the other side operates with no apparent guardrails."
A Polymarket spokesperson responded to Mansour's comments by quoting Emerson: "The louder he talked of his honor, the faster we counted our spoons." The spokesperson also stated the platform has robust insider trading screening mechanisms, having referred suspicious leads to law enforcement nearly a hundred times, and emphasized, "We are committed to building a precise, fair, and transparent trading market."
As prediction markets move from a niche sector to mainstream popularity, regulatory pressure on both companies continues to mount. Attorneys general from multiple states have sued both platforms, alleging their sports betting businesses violate gambling laws; Polymarket is also under investigation by the U.S. Commodity Futures Trading Commission (CFTC).
Kalshi's reporting on Polymarket has become more direct. In May, former CFTC commissioner and current Kalshi board member Brian Quintenz posted on X about Polymarket's user verification mechanisms, tagging the official account of the U.S. Attorney's Office for the Southern District of New York.
The History of the Feud
Coplan, a native New Yorker, founded Polymarket in 2020, initially working from an apartment in Lower Manhattan with a bathroom converted into an office and a single laptop. Back then, he saw himself as an industry newcomer pioneering a completely unconventional product.
He soon faced a formidable opponent. Mansour, who grew up in Lebanon and was a former trader at Citadel, co-founded Kalshi in 2018 with MIT classmate and current company COO Luana Lopes Lara. Colleagues describe Mansour as brilliant, driven, and somewhat reserved; Coplan is personable, collects art, loves music, and embodies a relaxed, free-spirited New Yorker vibe.
Luana Lopes Lara, Kalshi Co-founder
Their relationship was never friendly. Sources recall an awkward early meeting where Coplan mentioned both were raised by single mothers, a comment that made Mansour deeply uncomfortable.
But they shared one conviction: prediction markets would reshape finance and media, using "the wisdom of crowds" to produce highly valuable informational references. Both Polymarket and Kalshi present bets as yes/no questions on topics ranging from weather to the Super Bowl. The total amount users wager determines the odds for a given event.
Kalshi applied for a full operating license from the CFTC long before launching its betting business in 2021. Three people familiar with the matter revealed that even during early communications with regulators, Kalshi raised compliance concerns about Polymarket.
The main point of contact was Kalshi strategic advisor Jeff Bandman, who repeatedly urged the CFTC to scrutinize Coplan's company, pointing out that the platform was accessible in the U.S. without a license. In January 2022, the regulator fined Polymarket $1.4 million and ordered it to stop accepting bets from U.S. users.
This ban briefly gave Kalshi a chance to dominate the U.S. market, but the company still had to negotiate with regulators for more favorable rules. During the Biden administration, the CFTC banned election betting, leading Kalshi to sue the agency in 2023.
While Kalshi was embroiled in litigation, Polymarket exploded in popularity even though it was banned from serving U.S. users. American users could simply use a VPN to change their location and access the offshore website. Ahead of the 2024 presidential election, the platform's odds sparked widespread discussion online, showing a much higher probability of a Trump victory than traditional polls.
Mansour said bluntly on a podcast in June, "They completely skipped the compliance process, launched the product, and had no qualms."
On the eve of the election, Kalshi won its court case, allowing licensed prediction markets to operate legally in the U.S. Polymarket still lacked a domestic license, but its traffic soared, and Coplan became a celebrity in the industry.
In 2024, the U.S. Attorney's Office for the Southern District of New York launched an investigation into whether Polymarket was illegally accessible to U.S. users. A week after Trump's victory, the FBI raided Coplan's Manhattan apartment, seizing all electronic devices.
Kalshi immediately seized the opportunity. Tech media "Pirate Wires" exposed chat screenshots showing Kalshi employee Keaton Inglis contacting former NFL star Antonio Brown, instructing him to post on X that Coplan was "guilty."
Antonio Brown, Former NFL Star
Brown later apologized, stating he was in a business partnership with Kalshi at the time and had casually reposted the content. Mansour also apologized, saying on a podcast in December 2024, "Some members of our team got overly emotional."
The raid made Coplan and his team deeply suspicious, and rumors quickly spread through the media. Four people familiar with the matter revealed that Polymarket privately speculated Kalshi or its associates had hired private investigators to follow Coplan, who then tipped off the media after witnessing the FBI raid.
Kalshi spokesperson Diana dismissed this: "This is completely baseless. Their fantasies have reached absurd levels."
Sabotaging a Major Deal
Last July, Coplan went to a crucial business dinner at Manhatta, a top-floor restaurant in Manhattan with 60th-floor panoramic views. He dressed casually, carrying a bagel in a paper bag.
The other party at the dinner was billionaire Jeffrey Sprecher, founder of Intercontinental Exchange (ICE). This $80 billion giant operates the New York Stock Exchange. The meeting between the old-guard titan and the new-sector disruptor marked a key turning point in the Polymarket-Kalshi rivalry.
For years, Kalshi had backing from top-tier VCs like Sequoia Capital; Coplan had repeatedly struck out when pitching to large institutions. But both Coplan and Mansour were courting investment from ICE, which was interested in the prediction market space.
Coplan and Sprecher hit it off. ICE, which had been considering an investment in Kalshi, ultimately signed an investment agreement with Polymarket in the fall of last year.
According to sources, Mansour was furious upon learning the news. Five people familiar with the matter said that before the deal was announced, Mansour and Kalshi investor Alex Immerman, a partner at a16z, separately met with ICE's senior management team.
Descriptions of the conversation details vary among sources, but three confirmed that Mansour and Immerman's communications essentially amounted to using every means to dissuade ICE from making the investment.
Kalshi spokesperson Diana stated the company itself "had no intention of pursuing a deal with Sprecher."
Jeffrey Sprecher, Founder of Intercontinental Exchange
Sprecher ultimately bet on Coplan, announcing in October an investment of up to $20 billion in Polymarket. This was just one in a series of wins for Polymarket: in July last year, the Trump administration's shift in enforcement priorities led the Southern District to drop its investigation into Coplan; later that summer, Donald Trump Jr.'s venture firm, 1789 Capital, also announced an investment in Polymarket.
Coplan said on "60 Minutes" last year, "This administration is very pro-innovation, pro-crypto, and particularly pro-Polymarket, which is incredibly rare."
To capitalize on the policy shift, Polymarket needed a U.S. operating license. Coplan planned to acquire a company that already held compliant credentials.
He again ran into opposition from Kalshi. Five people familiar with the matter said rumors circulated that Coplan was interested in acquiring the niche prediction platform Railbird. Mansour then reported potential issues with that acquisition target to senior CFTC officials.
Kalshi's report didn't work. In June 2025, the CFTC approved Railbird's operating credentials. Coplan ultimately spent $112 million to acquire another licensed company, QCX. Although the offshore main platform remained restricted, the acquisition of QCX allowed Polymarket to launch a lightweight U.S. domestic app, reaching a massive domestic user base.
Announcing the acquisition in July, Coplan posted a picture of the American flag on social media with the caption: "Been waiting for this day for far too long. Polymarket is officially back in the USA."
Deliberately Provocative Business Moves
This spring, when the New York Knicks made the playoffs, Mansour posted a courtside photo from Madison Square Garden, wearing team colors and grinning.
Officially, this was a celebration of a new partnership between Kalshi and the arena, with the sixth-floor promenade officially named the Kalshi Promenade. But industry observers saw another layer: a deliberate provocation.
Coplan frequently shared Knicks-related content on social media before his fame and was a regular courtside presence during the regular season. Sources said Polymarket had also been negotiating a similar sponsorship before Kalshi secured the deal but was unwilling to match the offer Kalshi presented.
This also signified that an industry feud once confined to the niche crypto circle had fully entered the mainstream spotlight. In the first six months of this year, the total transaction volume of the two platforms exceeded $150 billion, a 1200% increase, undoubtedly intensifying the competition.
Based on current data, Mansour is temporarily ahead. After a new funding round in May, Kalshi's valuation reached $22 billion, $7 billion higher than Polymarket's. According to data firm The Block, Kalshi's transaction volume last month was $33 billion, double that of Polymarket.
Diana denied that the Madison Square Garden partnership was aimed at Coplan: "We don't pursue business deals to antagonize competitors. That notion is laughable."
The surge in prediction market popularity has also attracted stricter regulatory scrutiny, with much of the focus falling on Polymarket. In April of this year, a U.S. Army Special Forces soldier was indicted for using classified information to bet on Polymarket's offshore platform via VPN on events related to the arrest of Venezuelan President Nicolás Maduro, illegally profiting over $400,000. A Polymarket spokesperson stated the platform explicitly prohibits VPN access.
The two platforms take截然不同的 approaches to controlling insider trading. Kalshi requires users to submit full personal information before betting, including their profession in some cases. All Polymarket trades are publicly visible on-chain, allowing the community to self-police for violations. Users of the U.S. domestic app must verify their identity, but the offshore main platform still does not mandate users to disclose private information like their name or workplace.
Polymarket-paid influencer Aj Pleasanton commented that this model is common in the crypto industry, where users generally prefer anonymity.
Privately, Mansour has grown increasingly frustrated with Polymarket's model. Two people familiar with the matter said he often calls Polymarket's Chief Legal Officer, Neal Kumar, to express his anger.
Conflicts between the two are frequent. According to sources and documents reviewed by The New York Times, in the spring of 2025, several influencers contracted by Polymarket widely spread news about Kalshi's failed partnership talks with Elon Musk's xAI.
That same year, Polymarket hired former early Uber employee Max Crowley as Vice President of Partnerships. Less than two months after joining, Crowley jumped ship to Kalshi, which infuriated Coplan. Sources said during the transition, Coplan and company board lawyer Alex Spiro sent a threatening legal letter to Crowley, but no lawsuit was ultimately filed.
Even when facing common industry challenges, the two companies refuse to cooperate. Kalshi formed an industry lobbying group to fight restrictive prediction market regulations in various states, uniting several competitors but explicitly excluding Polymarket.
The month after Kalshi suffered a legal loss in a state sports betting lawsuit, Polymarket promptly launched a new betting market, allowing users to wager on when Kalshi's Massachusetts sports business would be shut down.
