In addition to landing his movement the imprimatur of a sitting member of Congress, Mr. Fuentes has gained a powerful defender. In May, the Arizona Republican wrote to the F.B.I. on his official letterhead accusing the agency of abusing its power to relegate individuals to the no-fly list, singling out Mr. Fuentes and claiming that other “constitutionalists” and “patriots” were also being unfairly targeted. Mr. Fuentes said that Mr. Gosar had been the only Republican lawmaker willing to do so. “Almost nobody from the Republican Party had anything to say about it or felt concern,” Mr. Fuentes said on his show, adding that his attempt meet up with Ms. Greene had been rebuffed by her team. The fringe is not an unusual place for Mr. Gosar. After the Capitol riot, he came under scrutiny for his ties to Ali Alexander, a far-right activist and conspiracy theorist who emerged as a leader of the “Stop the Steal” movement. Mr. Gosar frequently tagged him in Twitter posts, including ones urging his followers to “not accept a coup.”