Mr. Gaetz will hold a rally Thursday in Ms. Cheney‘s backyard as he campaigns for his colleagues to remove her as chairwoman of the House Republican Conference, the party’s third-highest position in the chamber.

Donald Trump Jr. expressed regret that he can’t attend the event, but asked if he could “Skype or call in.”

In a tweet promoting the event in Cheyenne, Mr. Gaetz said, “I do not want her job. I unequivocally am not seeking a position in House Leadership. I also know Wyoming can do better.”

Mr. Gaetz also urged people to call their representatives and ask whether they favor removing Ms. Cheney.