“When you have a high-profile event like this, lots of people want to get in on the action,” said Mark Pitcavage, the senior research fellow for the Anti-Defamation League’s Center on Extremism. “It has the ability to draw all sorts out of the woodwork.”

Among them is David Fry, a 27-year-old Ohioan who has regularly posted homophobic and anti-Semitic messages on social media. Jon Ritzheimer, who is also camped out with the Bundys, is a Marine veteran from Arizona who drew national attention in May when he organized an anti-Islam protest at a mosque in Phoenix; the mosque had been attended by a pair of Muslim men who opened fire earlier that month at a “Draw Mohammad” contest in Garland, Tex.

There was also Pete Santilli, the conservative host of “The Pete Santilli Show,” who roamed about the refuge with a camera on a stick, cheering occupiers and heckling journalists.

Mr. Santilli spoke on his online radio show last spring about a “battle between heterosexuals and homosexuals” and once drew scrutiny from the Secret Service after saying he wanted to shoot Hillary Clinton.

At Malheur, he is working alongside people like Bruce Doucette, a computer technician who reportedly plans to seek indictments against federal officials and describes himself as a United States Superior Court judge — even though no such office exists.

“What we’re seeing is an amalgamation of a lot of different and disparate strands of the extremist movement converging in one place,” said Ryan Lenz, a senior writer for the Southern Poverty Law Center, which tracks and studies extremist groups. “Although they all have slightly separate agendas, they’ve come together in Oregon because of the same intense resentment of the government.”

According to Mr. Pitcavage, who has written an analysis of the philosophies behind the occupation, about a third of the protesters in Oregon were motivated, like the Bundys, by land-use issues that have bedeviled the West since the Sagebrush Rebellion of the 1970s.