SPRINGFIELD, Va. — When word surfaced in February that Senator Tom Coburn, Republican of Oklahoma, was plotting with Democrats on a bill to expand background checks for gun buyers, Larry Pratt got really mad. Then, Mr. Pratt, the executive director of Gun Owners of America, got busy, mounting a lobbying blitz that helps explain why a bipartisan Senate deal on background checks remains elusive.
Within days, his staff, working from a nondescript space in a squat office building off the Beltway here — there isn’t even a nameplate on the door — was on the phone with supporters of his organization in Oklahoma. The group’s members were encouraged to inundate Mr. Coburn with e-mails and calls and to otherwise make it exceedingly clear to the senator that an enhanced background check law would not be tolerated.
It wasn’t long until Mr. Coburn, a gun rights advocate, had backed away from negotiations with Senator Charles E. Schumer of New York, the No. 3 Senate Democrat, securing at least a temporary victory for gun rights activists and frustrating advocates of new gun safety laws.
Once largely unknown, Gun Owners of America, with its war chest, membership and lobbying strength dwarfed by the National Rifle Association, is emerging as an influential force as a series of gun control measures heads to the Senate floor.
The group has already been successful in both freezing senators, particularly Republicans, who have appeared to be on the fence about supporting bills to expand background checks and increase penalties for illegal gun purchases, and empowering those who have a strong gun rights background.
“They are strong defenders of the Second Amendment,” said Senator Ted Cruz, Republican of Texas, who received donations from the group during his primary campaign and is its key ally in the Senate.
Mr. Coburn attributed his retreat, which deeply damaged the prospects of the bill, to a plan that would have required private gun sellers to keep records. But the gun group believes its campaign contributed to his decision.
“His staff admitted that it kind of irritated the senator,” Mr. Pratt said. “We were told, ‘He’s getting tired of this.’ But when we hear complaints like that, we know we are close to success. We are happy he changed his mind.”
While it might be increasingly potent, the group is not rich.
Gun Owners of America’s total revenue in 2011 was less than $2 million, compared with the N.R.A.’s nearly $220 million. The group spent $1.3 million last year to lobby Congress, while the N.R.A. spent nearly $3 million. Its campaign contributions last year were $119,850, placing it at 2,669 on a list of 20,968 lobbying groups ranked by the Center for Responsive Politics. The N.R.A. spent $1.5 million, putting it at 230th. Gun Owners of America has 300,000 dues-paying members; the N.R.A. has five million.
But, like many grass-roots groups, it is loud. Its members pepper Republican lawmakers with calls. In Republican primaries, the group supports candidates that hew to its message, and it rates floor votes with criteria far tougher than the N.R.A.’s. Senator Max Baucus of Montana, one of the few Democrats to earn an A from the N.R.A., has a D-minus from the group. This is in part because it draws from a far broader range of past votes, like President Obama’s health care legislation, to judge lawmakers.
John Hart, a spokesman for Mr. Coburn, declined to respond to questions about the group’s role in the senator’s decision to pull away from negotiations over a background check bill. “No one in the Senate has a stronger record of not only defending but expanding Second Amendment rights,” Mr. Hart said, adding that “Dr. Coburn is still hopeful he can reach an agreement with Senator Schumer.”
Mr. Schumer said he hoped for the same. “In the area of guns there’s always political pressure,” he said. “But I know Tom Coburn well. He’s a very principled guy.”
Many lawmakers and gun safety advocates believe Gun Owners of America’s rising profile and heavy membership drive has led the N.R.A. to take a more aggressive stance against measures it once supported, like an expansion of background checks to include private gun sales. (In 1999, Wayne LaPierre, the chief executive of the N.R.A., said there should be “no loopholes anywhere, for anyone” on gun sale background checks.)
Part of the group’s mission, Mr. Pratt said, is to stay on top of the N.R.A. “when we don’t think they’ve gone far enough.”
“The N.R.A. is essentially a political party,” said Mark Glaze, the director of Mayors Against Illegal Guns. “The big majority is centrist, and the base is ideological. And they’re pulled to the right in a competition for the base with Larry Pratt, and that’s marginalizing them.”
Gun Owners of America’s central mission now is to prevent the passage of several bills about to hit the Senate floor. It is also lobbying for a House bill that would eliminate gun-free school zones.
Democratic aides said that Republicans approached to co-sponsor a background check bill cited Mr. Pratt’s group as their biggest impediment, fearing retribution. Senator Dean Heller of Nevada worried about the group, aides say; Mr. Pratt said his group was concerned about Mr. Heller. “He’s been kind of wandering around,” Mr. Pratt said.
Mr. Heller said that the group “is a group that I respect,” adding that he believed Congress “should expand background checks,” but had declined to support a bill with Mr. Schumer. His spokesman did not respond to more requests about Mr. Heller’s relationship with the group.
Gun Owners of America was formed in 1975 partly in response to the 1968 gun control act — “to oppose the government,” Mr. Pratt said. The N.R.A., he said, was founded to work with the government on issues like marksmanship. (The N.R.A. declined to comment.)
Mr. Pratt cited the groups’ positions on a 2007 bill that limited gun access to members of the military with post-traumatic stress disorder, which his group opposed and the N.R.A. did not.
Mr. Pratt, 70, has long been active in Republican politics. He served in the Virginia legislature in the 1980s, and he worked briefly for Patrick J. Buchanan’s 1996 presidential campaign.
His group’s positions tend to veer farther right than those of the N.R.A. Instead of expanding background checks, he would like to unravel the existing ones on gun purchases, fearing they will lead to a national gun registry. “We have opposed them from the beginning,” he said, “because there will be mission creep.”
Mr. Pratt’s group also opposes penalties for so-called straw purchases, or sales made to people who intend to sell or give the weapon to a person who cannot pass a background check. “There would not be straw purchasing if there were no limits on who can carry a gun,” he said.
Kitty Bennett contributed research.