A business war that pushes the boundaries of ethical boundaries.
Written by: David Yaffe-Bellany and William K. Rashbaum, The New York Times
Compiled by: Luffy, Foresight News
One November morning in 2024, Polymarket founder Shayne Coplan woke up to find his home invaded by several FBI agents armed with a sledgehammer. They searched his New York apartment for evidence related to the platform's illegal gambling activities.
Coplan publicly stated on social media that the search was a politically motivated crackdown by the Biden administration. However, privately, he and his team of advisors harbored other suspicions and blamed Polymarket's numerous troubles on Tarek Mansour, CEO of its biggest competitor, the prediction market platform Kalshi.
Four sources familiar with the matter revealed that months before the FBI raid, Kalshi's lawyers visited the Manhattan federal prosecutor's office to file a complaint about Polymarket, a matter that had never been publicly disclosed before. The sources said the lawyers detailed Polymarket's operating model to prosecutors, highlighting a key issue: the platform should have been banned in the United States, but users could still access it normally.
This standoff is simply the culmination of a long-standing feud between Kalshi and Polymarket. Both companies represent some of the hottest startups in the tech industry today. Clashes of ambition between Silicon Valley founders are nothing new; industry battles fueled by arrogance are commonplace, such as Uber and Raffles vying for the ride-hailing market. The public spat between billionaires Sam Altman of OpenAI and Dario Amodei of Anthropic has also become a compelling subplot in the artificial intelligence industry.
However, the rivalry between 28-year-old Coplan and 30-year-old Mansour has long since crossed the boundaries of normal business competition. More than forty people from both sides, speaking anonymously in interviews, said that the two, both newly minted billionaires, are determined to monopolize the prediction betting market covering all categories including sports, politics, and entertainment, and they have an extreme mutual dislike for each other. This antagonism has permeated almost all business dealings between the two companies.
Shayne Coplan, founder of Polymarket
Dustin Gouker, a longtime columnist on the prediction market industry, said: "The animosity between the two sides runs deep, and the struggle has long been mixed with personal grudges."
This battle spilled over into internal corporate meetings and U.S. Congressional hearings, influencing the direction of regulatory policy in Washington and sparking unprecedented industry attention and regulatory concerns. The two companies engaged in trademark squatting, vying for the same business partnerships, poaching each other's talent, exchanging accusations in the media, and launching direct personal attacks on social media. Both had established business partnerships with Donald Trump Jr., a common public relations strategy in Washington during Trump's presidency.
Noah Zingler-Sternig, a former Kalshi employee and manager of a prediction market investment fund, commented: "Both companies have overstepped their bounds in many ways, making it difficult for the public to take these two platforms seriously."
The animosity between the two companies goes beyond a battle for market share; the deeper disagreement lies in their bottom lines and business ethics. Kalshi cultivates an image of compliance, insisting on obtaining US regulatory approval before commencing domestic operations; Polymarket, on the other hand, has not obtained a domestic license, and its core platform has long operated offshore. Kalshi strictly enforces real-name authentication rules and blocks sensitive betting categories; Polymarket users can register without submitting personal information and can even bet on events such as the timing of an Israeli missile attack.
Although Coplan and Mansour have met occasionally over the years, they now barely interact, only exchanging insults. Mansour, a graduate of MIT and a self-proclaimed math enthusiast, once compared the rivalry between the two companies to a healthy competition between two legendary quarterbacks, Tom Brady and Eli Manning. However, recently he stated that Polymarket's operating model is "illegal and unethical," pointing out that its offshore platform is operated by a Panamanian entity.
In April of this year, Mansour publicly stated at an industry conference in Washington: "I don't know what regulations Panama has regarding insider trading in prediction markets, and it's highly likely there are no such restrictions at all."
Coplan, a dropout from NYU, is known for his charismatic pitches and rarely mentions Kalshi in public. However, two sources familiar with the matter revealed that he privately claims Kalshi simply copied the Polymarket model and believes Mansour has been trying to suppress him. Coplan firmly believes his platform is the best solution in the industry, stating on the 60 Minutes program last year, "This is the most accurate information tool that mankind currently possesses."
Kalshi spokesperson Elisabeth Diana stated that the company learned of the FBI search through news reports. She added that Kalshi routinely communicates with regulatory agencies regarding compliance issues and has publicly stated that "some companies are harming user rights and damaging the industry's reputation."
Tarek Mansour, co-founder of Kalshi
Diana stated, "Mansour himself has no personal animosity towards Shayne. His only complaint is that Kalshi has spent years promoting industry compliance, while Shayne operates the track in a completely unscrupulous manner."
A Polymarket spokesperson responded to Mansour by quoting Emerson: "We should keep a close eye on the spoons of those who proclaim themselves to be of high moral character." The spokesperson added that the platform has established a robust insider trading screening mechanism, having transferred suspicious leads to law enforcement nearly a hundred times, and emphasized: "We are committed to creating an accurate, fair, and transparent trading market."
As prediction markets have transitioned from a niche market to mainstream popularity, the two companies are facing increasing regulatory pressure. Attorneys general from multiple states across the U.S. have filed lawsuits against the two platforms, accusing their sports betting operations of violating gambling regulations; Polymarket is also under investigation by the U.S. Commodity Futures Trading Commission (CFTC).
Kalshi's whistleblowing on Polymarket has become increasingly direct. In May, Brian Quintenz, a former CFTC commissioner and current Kalshi director, published an article on the X platform introducing Polymarket's user moderation mechanism and tagging the official account of the U.S. Attorney's Office for the Southern District of New York.
The ins and outs of the feud between the two rivals
Coplan is a native New Yorker who founded Polymarket in 2020. Initially, he worked in an apartment in Lower Manhattan, with the bathroom temporarily converted into an office, and a laptop was all the equipment he had. At the time, he considered himself a newcomer to the industry, pioneering a completely unconventional product.
He soon faced formidable competition. Mansour, who grew up in Lebanon, was a trader at Citadel Fund and co-founded Kalshi in 2018 with his MIT classmate and current COO, Luana Lopes Lara. Colleagues described Mansour as intelligent, adventurous, and somewhat introverted; Coplan, on the other hand, was easygoing, an art collector, a music lover, and possessed the relaxed and carefree spirit of a New Yorker.
Luana Lopes Lara, co-founder of Kalshi
The two had never had a friendly relationship. An insider recalled that during an awkward meeting years ago, Coplan mentioned that they were both raised by single mothers, a remark that made Mansour very uncomfortable.
However, both share a consensus: prediction markets will reshape the financial and media industries, relying on "collective intelligence" to produce highly valuable information. Both Polymarket and Kalshi use "yes/no" questions for betting, with betting options covering topics such as weather and the Super Bowl. The total amount wagered by users determines the odds for the corresponding event.
Kalshi applied for a full operating license from the CFTC even before launching its betting business in 2021. Three sources familiar with the matter revealed that Kalshi had already raised compliance issues with Polymarket with regulators during the initial communication phase.
The primary contact person was Jeff Bandman, a strategic advisor at Kalshi, who repeatedly urged the CFTC to investigate Coplan's operations, pointing out that the platform could operate in the United States without a license. In January 2022, the regulator fined Polymarket $1.4 million and ordered the platform to stop accepting bets from U.S. users.
This ban initially gave Kalshi the potential to monopolize the US domestic market, but the company still needs to negotiate with regulators to secure more lenient operating rules. During the Biden administration, the CFTC banned election betting, and Kalshi sued the regulator in 2023.
Even while Kalshi was embroiled in legal battles and banned from serving US users, Polymarket continued to thrive. US users could access the offshore website simply by using a VPN to change their location. Before the 2024 presidential election, the platform's odds sparked widespread discussion online, with data showing Trump's probability of winning significantly higher than traditional polls.
In a podcast appearance in June, Mansour bluntly stated, "They completely skipped the compliance process and launched their product directly without any scruples."
On the eve of the election, Kalshi won a court case, allowing licensed prediction markets to legally operate in the United States. Polymarket still lacked local operating qualifications, but its platform traffic skyrocketed, and Coplan instantly became a celebrity in the industry.
In 2024, the U.S. Attorney's Office for the Southern District of New York launched an investigation to determine whether Polymarket had violated regulations by providing services to U.S. users. A week after Trump's election victory, the FBI raided a Coplan Manhattan apartment and seized all electronic devices.
Kalshi immediately seized the opportunity to generate publicity. Tech media outlet Pirate Wires released chat screenshots showing that Kalshi employee Keaton Inglis contacted former NFL star Antonio Brown, instructing him to post on the X platform that Coplan was "guilty."
Antonio Brown, former NFL star
Brown later issued an apology, stating that he was working with Kalshi at the time and casually forwarded the content. Mansour also apologized, stating in a December 2024 podcast, "Some of our team members were overly emotional at the time."
The search fueled suspicions within Coplan and his team, and related rumors quickly spread through the media. Four sources familiar with the matter revealed that Polymarket privately speculated that Kalshi or his partners had hired private investigators to follow Coplan and, upon witnessing the FBI's visit, immediately informed the media.
Kalshi spokesperson Diana refuted this, saying, "This is complete nonsense; the other party's imagination has reached an absurd level."
Secretly sabotage a major collaboration
Last July, Coplan attended a key business dinner at Manhatta, a rooftop restaurant in Manhattan with panoramic views from the 60th floor. He was dressed casually and carried a bagel in a paper bag.
The other party at the dinner was billionaire Jeffrey Sprecher, founder of the Intercontinental Exchange (ICE). This $80 billion giant operates the New York Stock Exchange. This meeting between giants from both the old and new sectors marks a key turning point in the competition between Polymarket and Kalshi.
For years, Kalshi has had top-tier venture capital investors like Sequoia Capital; Coplan, on the other hand, has repeatedly failed to secure funding from large institutions. However, both Coplan and Mansour are vying for investment from the Intercontinental Exchange, a giant interested in entering the prediction market arena.
Coplan and Sprecher hit it off immediately. Intercontinental Exchange, which had initially considered investing in Kalshi, ultimately finalized its investment agreement with Polymarket last fall.
Sources familiar with the matter said Mansour was furious upon learning the news. Five sources revealed that prior to the official announcement of the partnership, Mansour and Alex Immerman, a partner at Kalshi's investor a16z, separately met with the Intercontinental Exchange's senior management team.
Several sources familiar with the matter gave differing accounts of the conversation, but three confirmed that Mansour's communication with Immerman was essentially an effort to dissuade the Intercontinental Exchange from abandoning the investment.
Kalshi spokesperson Diana stated that the company itself "has no intention of pursuing a partnership with Sprecher."
Jeffrey Sprecher, founder of Intercontinental Exchange
Ultimately, Sprecher chose to bet on Coplan, officially announcing in October an investment of up to $2 billion in Polymarket. This is just one of the many positive developments Polymarket has received: last July, the Trump administration tightened law enforcement standards, and the Southern District of New York dropped its investigation into Coplan; that same summer, Donald Trump Jr.'s venture capital firm 1789 Capital also announced an investment in Polymarket.
Coplan said on the 60 Minutes program last year: "This administration is giving strong support to innovation and the crypto industry, especially to Polymarket, which is very rare."
To capitalize on policy benefits, Polymarket must obtain a U.S. operating license. Coplan plans to acquire a company that already holds the necessary qualifications.
He encountered Kalshi's obstruction once again. Five sources familiar with the matter revealed that rumors circulated that Coplan intended to acquire the niche prediction platform Railbird, and Mansour subsequently reported the potential risks of the acquisition to senior CFTC officials.
Kalshi's complaint was unsuccessful, and in June 2025, the CFTC approved Railbird's operating license. Coplan eventually spent $112 million to acquire another licensed company, QCX. Although the offshore main platform remained restricted, after acquiring QCX, Polymarket launched a lightweight US app, allowing it to reach a massive number of local users.
When Coplan officially announced the acquisition in July, it posted a picture of the American flag on social media with the caption: "I've waited too long for this day. Polymarket is officially back in the United States."
Deliberately provocative business games
This spring, when the New York Knicks made the playoffs, Mansour posted photos of himself watching a game at Madison Square Garden, wearing team-colored clothing and grinning broadly.
Officially, this was a celebration of a new partnership between Kalshi and the arena, with the sixth-floor corridor officially named the Kalshi Corridor. However, industry observers saw another layer of meaning: a deliberate provocation.
Before Coplan became famous, he frequently shared Knicks-related content on social media and was often seen courtside at games during the regular season. Sources revealed that Polymarket had also approached Coplan for similar sponsorships before Kalshi finalized the deal, but was unwilling to match Coplan's offer.
This also marks the complete public emergence of the industry battle, which was originally confined to the niche crypto community. In the first six months of this year, the total transaction volume of the two platforms exceeded $150 billion, an increase of 1200%, which undoubtedly intensified the competition.
Based on current data, Mansour is temporarily in the lead. After completing a new round of financing in May, Kalshi's valuation reached $22 billion, $7 billion higher than Polymarket. According to data agency The Block, Kalshi's transaction volume last month was $33 billion, twice that of Polymarket.
Diana denied that the partnership with Madison Square Garden was intended to target Coplan: "It's ridiculous to suggest that we would finalize a business partnership to provoke a competitor."
The surge in popularity of prediction markets has also attracted stricter regulatory scrutiny, with most of the focus on Polymarket. In April of this year, a U.S. special forces soldier was indicted for using classified information and a VPN to access the Polymarket offshore platform to bet on the arrest of Venezuelan President Maduro, illegally profiting over $400,000. A Polymarket spokesperson stated that the platform explicitly prohibits VPN access.
The two platforms have drastically different approaches to controlling insider trading. Kalshi requires users to submit complete personal information before placing bets, and in some cases, also requires them to disclose their occupation; Polymarket publishes all transactions on-chain, making it easy for community users to self-check for violations. While users of the US-based app must register with their real names, the offshore main platform still does not force users to disclose private information such as their name and workplace.
Polymarket paid influencer Aj Pleasanton commented that this model is very common in the crypto industry, where users generally prefer to operate anonymously.
Privately, Mansour was increasingly dissatisfied with Polymarket's operating model. Two sources familiar with the matter revealed that he frequently called Polymarket's Chief Legal Officer, Neal Kumar, to express his anger.
The two sides have frequently clashed. According to sources and documents reviewed by The New York Times, in the spring of 2025, several influencers signed with Polymarket widely spread the news that Kalshi's collaboration with Elon Musk's xAI had broken down.
That same year, Polymarket hired Max Crowley, an early Uber employee, as Vice President of Partnerships. Less than two months later, Crowley jumped ship to Kalshi, infuriating Coplan. Sources say that during the period between job changes, Coplan and the company's board lawyer, Alex Spiro, sent him a lawyer's letter threatening to sue, but no case was ultimately filed.
Even though they shared common industry interests, the two companies refused to cooperate. Kalshi formed an industry lobbying group to fight against restrictive regulations on forecast markets enacted by various states, uniting with many peers, but excluding Polymarket.
The following month, Kalshi lost a sports betting lawsuit in a state, and Polymarket immediately launched a new betting platform, allowing bets on when Kalshi's Massachusetts sports operations would shut down.