A high-stakes Republican primary race in Kentucky has emerged as a critical test case for a question roiling the U.S. conservative movement: can a GOP candidate win elected office while openly clashing with former President Donald Trump? At the center of this fight is Thomas Massie, the incumbent congressman who gained national attention earlier this year for spearheading efforts to force the release of previously sealed court documents connected to the Jeffrey Epstein case. Now, Massie faces a fierce challenge from a political opponent who has secured the full endorsement and active support of Trump, a move that has amplified national attention on this down-ballot contest. The race is being closely watched by political strategists across the ideological spectrum, as it will offer key insights into the depth of Trump’s hold over the modern Republican Party. For years, intra-GOP challengers backed by Trump have ousted incumbent lawmakers who broke with the former president on key issues, from policy to personal loyalty. Massie’s high-profile push to unseal the Epstein files, a move that has put pressure on political figures from both major parties, has made him a test case for whether GOP voters will still back an incumbent who has not aligned fully with Trump’s agenda and political preferences. The outcome of the primary will have ripple effects for future GOP contests, as incumbent lawmakers weigh the political risks of breaking with the party’s dominant figure ahead of the 2024 election cycle.