Traders on prediction marketplaces like Polymarket and Kalshi are increasingly betting against Rep. Thomas Massie (R-Ky.), who President Donald Trump has dubbed the "worst Republican congressman in history."
A Polymarket poll with over $1.4 million in assets places Massie's odds in Tuesday's primary at 49%, down from 80% earlier this month. Ed Gallrein, who Trump has endorsed, has a probability of 52%.
The same is happening on Kalshi, where a poll with over $4 million in assets places Massie's odds at 49% and Gallrein's at 53%. Gallrein has been in a steady increase since May 5, when his odds were at 22%.
Official polls suggest that Tuesday's race will be close. A SoCal Strategies poll conducted between May 15 and 16 places Gallrein's lead at 7 points, while a Neighborhood Research Corporation poll has it at even. A Big Data Poll gives Massie a 1-point lead, while Quantus Research has Gallrein ahead by 8 points.
The Most Expensive Primary and a Referendum on Trump
The race to become the next representative for Kentucky's 4th Congressional District has become the most expensive one in the United States. Data shows that the two candidates have raised $25 million, with outside groups providing most of the funds.
Trump, who won the district by 33 points, has gone to war against Massie, calling him disloyal and arguing that he is the worst Republican Congressman in US history. Trump argues that Massie always votes against the Republican Party. However, historically, Massie votes nearly 90% in line with the party. His votes against it are typically on spending and foreign wars.
Trump's main beef with Massie is mostly because he was the main sponsor of a bill that forced the Department of Justice to release the Epstein files. Massie has also been a regular critic of Trump's Iran war.
Gallrein's odds of beating Massie jumped after Sen. Bill Cassidy (R-La.) lost his primary on Saturday. Cassidy was one of the seven senators who voted to impeach Trump for the January 7 events.
Trump's endorsed candidates have also scored some major victories this cycle. For example, Trump-backed candidates recently won the majority of GOP races in Indiana.
