WASHINGTON -- When Democrats acted last month to give the District of Columbia long-denied voting rights in Congress, the powerful gun lobby saw a target too good not to take a shot at.
The National Rifle Association's lobbyists made it clear to lawmakers that they believed the bill should include a measure to overturn the capital's gun control laws. Left mostly unsaid, but well understood by all 535 members of the House and Senate, was that failure to do so would unleash a barrage of political pain on resisters.
The result showed the strong sway the NRA has even over a Congress dominated by liberal Democrats who mostly disagree with the organization's positions. The Senate voted overwhelmingly to add the gun-rights proposal. House Democratic leaders, fearing a tough vote on the issue, swiftly scrapped plans to consider the D.C. voting legislation.
The bill hasn't resurfaced because Democrats cannot figure out how to keep it from splitting their ranks. Moderates and conservatives don't want to buck the NRA. Liberals are reluctant to be blackmailed into loosening gun laws.
The 138-year-old group derives its influence from a large and motivated base of members, particularly in rural areas and the South.
Its much younger political arm, set up in 1975, wields a carefully honed system for grading lawmakers and candidates based on how often they side with the NRA's legislative priorities. Their lobbyists tell lawmakers that they will be "scoring" specific bills -- the equivalent of saying, "We're watching you, and if you vote the wrong way, there will be consequences."
That scoring system helps determine which candidates the group supports in campaigns. That decision can be an important factor in elections.
The group's political action committee spent $15.6 million on campaign donations during the past two years, according to disclosures filed with the Federal Election Commission. The lion's share of the money went to challenging gun control advocates, especially President Barack Obama. The rest went to support strongly pro-gun candidates.
The NRA generally avoids contributing to lawmakers who don't vote with it. Many other organizations cultivate relationships with Congress by spreading their campaign cash around even to leaders and committee heads who don't always back their causes.
"The power of the NRA is in the millions of members all over the country who believe strongly in their freedom and their willingness to fight for it," said Chris W. Cox, the group's chief lobbyist.
Many, if not most NRA members give the group's ratings an enormous amount of weight on Election Day. "The political reality ... is that gun control's a loser," Cox said. If lawmakers "vote wrong on guns, history has shown they lose."
In the case of the voting rights bill, for example, the NRA quietly put out the word that it would score a procedural measure to set ground rules for the debate -- and determine whether the anti-gun control proposal could or could not be offered. That meant a vote to advance the bill without reversing the district's gun laws could cost a lawmaker the NRA's political support. It was enough to halt the measure in its tracks.
The following week, House Democratic leaders saw a wilderness conservation measure defeated after they tried to push it through under expedited procedures to avoid a contentious vote on gun rights. The measure passed Congress on Wednesday, only after House and Senate leaders agreed to a provision to placate the NRA through language by Rep. Jason Altmire, D-Pa., clarifying that the bill wouldn't impose new restrictions on hunting, fishing or trapping on federal land.
Gun control activists say they are baffled by the sway the gun lobby has over Congress. They argue the NRA no longer dictates election outcomes and that the group inflates its own importance.
"They operate on the principle of fear. They're trying to hold some mythical power from the early '90s over the heads of leadership that I think is totally irrelevant to what's going on today, but still has some long legs," said Paul Helmke of the Brady Campaign to Prevent Gun Violence.
Helmke said NRA's recent efforts to demonstrate its clout are partly "a sign of desperation. They realize this is probably their last gasp in terms of trying to be the force that they used to be."
Backers, however, argue that the group is growing in influence now that former President George W. Bush, a strongly pro-gun president, has been replaced with Obama. The former Illinois senator gets an "F" rating from the group despite his stated support for Second Amendment rights.
"Right now, they're having to play a lot more defense than they ever have before, and so the NRA membership around the country is more engaged," said Rep. Dan Boren, D-Okla., an NRA board member and a co-chair of the newly formed Second Amendment Task Force in Congress.
Democratic leaders are increasingly aware of that, particularly because many of their new members who are responsible for handing the party their majority are either strongly pro-gun or from states and districts where gun rights is a major issue.
"Democrats want to stay in the majority, and one of the ways to keep us in the majority is not to tilt toward gun control," Boren said.
The task force recently wrote Obama and House Speaker Nancy Pelosi, D-Calif., warning against any attempt to reinstate a ban on the sale of assault weapons.
Attorney General Eric Holder said last month that the Obama administration wanted to bring back the expired ban. It gave the NRA and other gun rights groups an important tool that fuels the work of countless Washington interest groups: a tangible threat with which to motivate supporters.
Gun rights groups are also increasingly worried that an outbreak in violence at the U.S.-Mexico border could pave the way for a raft of new gun control measures.
"We certainly expect to have defensive fights, and those are fights that were ready for," Cox said.