A fierce rivalry between the leaders of two prominent prediction market companies, Polymarket and Kalshi, has escalated into a highly personal and acrimonious dispute, according to reports. Shayne Coplan, the 28-year-old CEO of Polymarket, and Tarek Mansour, the 30-year-old CEO of rival Kalshi, are reportedly engaged in a feud characterized by personal attacks and the dissemination of unverified gossip.
Coplan, who has a net worth of $1 billion, has expressed frustration that Kalshi, which he has called a "copycat Polymarket," has surpassed his company in size. Sources claim Kalshi also alerted federal authorities prior to an FBI raid on Coplan's apartment in November 2024, as part of an investigation into allegations that Polymarket facilitated illegal gambling. Coplan was not arrested or charged following the seizure of his electronic devices.
The animosity between the two CEOs has reportedly become deeply personal. Insiders allege that Coplan refers to Mansour with the diminutive nickname "Little Tarek," referencing his height. Coplan has also allegedly circulated an unconfirmed rumor that Mansour and Kalshi's No. 2 executive, Luana Lopes Lara, were romantically involved and that their relationship ended due to Lopes Lara's infidelity. A Kalshi spokeswoman denied these claims, stating that Lopes Lara has never cheated on anyone and urged Coplan to focus on his company rather than spreading lies.
Sources indicate that Coplan has amplified the rumor, claiming at social events and in company meetings that Lopes Lara "cucked" Mansour, leading to their breakup. Coplan has also reportedly mocked Mansour to colleagues, calling him a "loser" for continuing to work with Lopes Lara after the alleged infidelity.
A spokesperson for Polymarket denied that Coplan has spread sexual rumors, asserting that Kalshi has fueled tensions between the companies for years and suggested that such allegations are an unfortunate outcome of Kalshi's efforts to dig up damaging information on Polymarket.
Mansour and Lopes Lara, who met at MIT, co-founded Kalshi in 2018. Lopes Lara recently announced her marriage to the "love of her life" on social media, and there has been no public indication that she and Mansour were ever romantically involved after college. Lopes Lara is noted for her background as a math prodigy and former ballerina before becoming a self-made billionaire.
Coplan has also reportedly experienced outbursts of anger, particularly upon learning of Kalshi's successes. He allegedly reacted with fury when Donald Trump Jr. joined Kalshi as a strategic advisor. Trump Jr. later also became an advisor and investor in Polymarket.
Reports suggest Coplan can be a demanding manager, with a source describing him as a manager focused on control rather than being a "chill" boss. He has reportedly been known to yell at employees over mistakes, missed market opportunities, and negative press.
Kalshi has reportedly surpassed Polymarket in trading volume, with approximately $31.5 billion traded on Kalshi in June compared to $10.6 billion on Polymarket, according to Dune Analytics. Polymarket, founded in 2020, has raised about $2 billion and was valued at $15 billion in a recent financing round. Kalshi has raised approximately $2.6 billion, with a valuation of $22 billion in May, and is reportedly in talks for further financing that could value it at $40 billion.