The mission of the S.R.A. is “to arm and train the working class for self-defense.”

It launched in its current form this spring — before that there was a Facebook group of the same name — and now has several hundred dues-paying members and over 30 chapters. This Monday, 28 new people joined, the group said.

Brad, a 36-year-old math professor, is a founder of the S.R.A.’s North Georgia chapter and a member of the S.R.A.’s central committee. “Some people are scared with what’s going on in the country right now,” he told me. He only recently started carrying a gun, after getting death threats for the socialist organizing he was doing in his small town. “People want to be able to protect themselves,” he said.

In the late 1960s and early 1970s, parts of the radical left fetishized firearms. Back then, some conservatives supported gun control as a way to disarm African-American militants; Ronald Reagan signed a bill banning open carry of loaded weapons when he was governor of California. “The Black Panthers and other extremists of the 1960s inspired some of the strictest gun control laws in American history,” the U.C.L.A. law professor Adam Winkler wrote in his book, “Gunfight: The Battle Over the Right to Bear Arms in America.”

Since then, however, gun culture has become virtually synonymous with American conservatism. The National Rifle Association is now perhaps the most powerful Republican lobby in the country, and its rhetoric increasingly echoes that of the apocalyptic far right. Over the last 20 or 30 years, Winkler told me, “not only has the N.R.A. become more and more associated with the right, but there’s an increasingly militaristic, rebellious tone to the N.R.A. and the gun rights movement.” It’s become, he said, “all about arming up to fight the tyranny that’s coming.”

Meanwhile, most of the left has embraced gun control, something that’s unlikely to change anytime soon. But it was probably inevitable that, as our politics have become more polarized and violent, a nascent left-wing gun culture would emerge.