“Join the MAGA crew,” said Greitens, a former Navy SEAL. “Get a RINO hunting license. “There is no baggage limit, no labeling limit and it does not expire until we save our country.” Mr. Greitens’ ad was just the latest, but perhaps the most threatening, in a long line of Republican campaigns that promote guns and equate hard-core conservatism with the use of deadly weapons. During a panel hearing Thursday, J. Michael Luttig, a former federal judge widely respected by conservatives, suggested that Mr. Trump and his allies posed a “clear and present threat to American democracy.” The use of violent rhetoric has been steadily increasing in Republican circles in recent months, as threats and aggressive images have become more common in community halls, congressional offices, and the election campaign. While much of the Republican’s violent speech and image creation is aimed at Democrats, some, as in Mr. Greitens’s advertisement, have focused on fellow members who are considered insufficiently conservative. On Sunday, spokesman Adam Kinzinger, an Illinois Republican and member of the Jan. 6 committee, published a letter to his wife from someone who had threatened to execute the couple. The Greitens campaign was not immediately available for comment on the ad. Mr Greitens has sought Trump’s approval, but so far without success. His campaign manager is Kimberly Guilfoyle, Donald Trump Jr.’s fiancée. Experts have warned that violent rhetoric can often lead to real physical violence. “When people feel more confident and lawful in expressing violent emotions, it can encourage others to feel more confident in facilitating real violence,” said Robert Pape, who studies political violence at the University of Chicago. “Unfortunately, this is a self-reinforcing spiral.” Some Republicans criticized Mr. Greitens for publishing the ad. “Every Republican should denounce this sick and dangerous ad by Eric Gretens,” Barbara Comstock, a former Virginia Republican, said Monday. “This is just a taste of the ‘clear and real danger’ that Judge Lutig spoke about last week.”