Mike Mazzei, a former Oklahoma state senator, won the Republican gubernatorial primary runoff on Tuesday with President Donald Trump's endorsement, defeating state attorney general Gentner Drummond and becoming the clear favourite to succeed term-limited Governor Kevin Stitt. The result also marks a political win for Stitt, who had long clashed with Drummond over lawsuits and public criticism, and reflects Trump's continued influence in shaping Republican primary outcomes across red states ahead of the 2026 elections.

Neither candidate reached the 50% threshold needed to win outright in the initial primary on 2 June, forcing the runoff between Mazzei and Drummond. Mazzei campaigned on eliminating Oklahoma's income tax within six years, cutting property taxes for seniors and veterans, and restricting foreign nationals from buying state land, while accusing Drummond of favouring tax rises and bigger government. Drummond, a rancher and former fighter pilot, pointed to his record as attorney general tackling illegal marijuana farms and pledged to support Trump on border security. The pro-business Club for Growth PAC, which spent $9 million backing Mazzei, hailed the win, while the feud between Stitt and Drummond had centred on the attorney general's pursuit of poultry companies over alleged water pollution.