Behind the scenes at the almost-sellout on background checks.

Thank God for GOA.

But a handful of smaller, more strident gun groups — most notably the Gun Owners of America and the National Association for Gun Rights — have continually attacked the N.R.A. for giving any ground, for negotiating with the enemy and, worst of all, for helping to elect lukewarm allies. By way of defending the organization’s strategy, Keene says: “The difference between the N.R.A. and a lot of these other gun organizations is that it’s easy enough to stand and say, ‘You shouldn’t compromise on anything.’ Our job is to actually get things done.”

Still, getting things done requires compromise, which is frowned upon by the group’s hard-core base. This dilemma has plagued the N.R.A. since it achieved passage of the 1986 Firearm Owners’ Protection Act, an N.R.A. triumph that came at a cost: to garner enough votes among Democrats, Wayne LaPierre, who then led the N.R.A.'s federal lobbying effort, agreed to a provision in the bill that banned the future sale of machine guns. Richard Feldman, an N.R.A. lobbyist back then and now its critic, said: “At the time, there was a huge controversy among the activist groups about the N.R.A. being a sellout. ‘They gave away your rights on machine guns!’ This was long before an Internet. Now it would be all over the place, and people would question what the N.R.A. did.”

That kind of instant, frenetic backlash is precisely what occurred during the spring of 2013, when word began to leak out that the N.R.A.'s top lobbyists were once again in the back room discussing gun legislation. On March 25, Dudley Brown, executive vice president of the National Association for Gun Rights, sent a mass email to thousands of gun enthusiasts that began: “It’s happening. . . . According to Politico, Sen. Joe Manchin is in secret negotiations with unnamed N.R.A. officials to sell out our gun rights. I’ve warned you from the beginning that our gravest danger was an inside-Washington driven deal.” In the email, Brown damningly referred to the deal as “the Manchin-N.R.A. compromise bill.”

A week later, on April 1, about 250,000 gun-rights sympathizers received an email from the Gun Owners of America, which promotes itself as “the only no-compromise gun lobby in Washington.” The email warned, “The media has been reporting that the N.R.A. is working” with Manchin. It concluded, “If you are an N.R.A. member, contact them,” and helpfully supplied the N.R.A. phone number, directing recipients to address their grievances to Wayne LaPierre.

The Gun Owners of America and the National Association for Gun Rights each has less than a tenth of the N.R.A.'s reported five million members and each has only one full-time lobbyist (the N.R.A. has more than a half-dozen federal lobbyists alone). Yet, as two people connected to the N.R.A. acknowledged to me, extreme gun groups can influence the N.R.A. simply by casting it as the establishment organization, much as Tea Party candidates have pushed mainstream Republican incumbents farther to the right. That would seem to be what occurred in the case of the Manchin-Toomey bill. For it was immediately following pressure from the hard-liners that the N.R.A. lobbyists suddenly and without notice backed away from the background-checks bill.

A few days after the Gun Owners of America’s mass email, Cox and Baker stopped communicating with Manchin’s office. (The N.R.A. denies that its withdrawal from the process was a result of pressure from other gun groups.)