Jeff Gunter, who is competing in Tuesday’s Nevada Republican primary for the Senate and described himself as “110 percent pro-Trump,” saw Donald J. Trump endorse one of his primary opponents, Sam Brown, over the weekend. He did not take it well.
Mr. Trump announced his endorsement of Mr. Brown on Truth Social, his social media platform, late Sunday night, after the former president’s rally in Las Vegas.
In a social media post on Monday, Mr. Gunter claimed without evidence, and without details, that a big political check had been sent from “the swamp,” amounting to a bribe for Mr. Trump.
He suggested that the former president had intended to endorse Mr. Brown at the rally, but refrained because of pressure from “fearless MAGA warriors.” Then a “big check” arrived, he claimed — possibly, he speculated, from the National Republican Senatorial Committee or a political action committee aligned with the Senate minority leader, Mitch McConnell — and prompted Mr. Trump to make the endorsement later.
Mr. Gunter’s campaign, when asked if the candidate could provide evidence that a donation had arrived before Mr. Trump announced his endorsement, responded, “Yes he can, stay tuned.” The campaign did not provide any evidence and did not respond to a question about when Mr. Gunter would do so.
Mike Berg, a spokesman for the N.R.S.C., said, “Jeff Gunter has become totally unglued and is making false, defamatory accusations against N.R.S.C. and President Trump’s team.”
The Senate Leadership Fund — the political action committee affiliated with Mr. McConnell, which Mr. Gunter appeared to refer to in his social media post — did not immediately respond to a request for comment on Tuesday.
Mr. Trump’s campaign pointed to a social media post on X from Chris LaCivita, a senior adviser to Mr. Trump, which read: “Proof Point as to why @DrJeffGunter didn’t earn the endorsement of @realDonaldTrump you have a habit of making up crap. President Trump makes his own decisions and this is another example of him choosing wisely.”
The Republican primary in Nevada on Tuesday will determine who faces Senator Jacky Rosen, the Democratic incumbent, in one of this year’s most competitive Senate races. The field is crowded: In addition to Mr. Gunter and Mr. Brown, an Army veteran who nearly died in Afghanistan, it includes Jim Marchant, a prominent election denier who lost an election for Nevada secretary of state in 2022, and several other candidates.
Mr. Gunter served in the Trump administration as U.S. ambassador to Iceland, which made Mr. Trump’s endorsement of his opponent sting. But Mr. Brown is leading in polls of the primary, and Mr. Trump has often jumped into races at the last minute to endorse the front-runner.