Rep. Kevin Hern’s March 2026 announcement for Oklahoma’s open U.S. Senate seat, following Sen. Markwayne Mullin’s confirmation as Homeland Security secretary and subsequent resignation, has produced overwhelming Republican primary consolidation behind the congressman. President Trump’s endorsement and Hern’s established fundraising network, congressional record, and alignment with state party priorities have minimized visible opposition from the minor candidates who filed by the April deadline. Traders reflect this dominance through a 95 percent implied probability for Hern ahead of the June 16 primary. A late high-profile entrant or sudden shift in major endorsements could still introduce competition, though no such developments have materialized in recent weeks.