WASHINGTON – A year of mass shootings climaxed with the murder of 26 people, including 20 children at a Newtown, Conn. school on Dec. 14, 2012. And from Dec. 15 through April 16 of 2013, 3,570 more Americans died from gunfire — victims of crime, suicide and accidents.

And yet, the next day, the U.S. Senate failed to pass legislation that would have imposed a renewed ban on assault weapons, added penalties for so-called straw purchasers, and limited the legal size of ammunition magazines. Those votes were largely symbolic, since the amendments faced stiff odds of getting all the way through tOrganization logoshis Congress.

More surprising that day was the failure of the Manchin-Toomey background check expansion, which in some national polls was supported by more than 80 percent of respondents.

Taken together, the votes seemed to reconfirm one of the most commonly held and oft-repeated beliefs in American politics: When it comes to gun policy, there’s no beating the National Rifle Association, which had lobbied heavily against the legislation.

A counter-narrative is developing, however, one portraying the power of the NRA as a self-fulfilling prophecy perpetuated by unsupported assumptions, not quantifiable evidence.

Both views of the NRA may be valid at once. While evidence of the gun lobby’s electoral impact is less compelling than assumed, the political class’ belief in the group’s power in electoral campaigns has historically given it significant legislative influence.

Even so, changes may be coming. As a re-energized gun control movement emerges, buoyed by the largess of groups like Mayors Against Illegal Guns and the shocking nature of recent shootings, the NRA could find itself challenged to a degree never before seen.

HOW MUCH IS REAL?

The NRA’s power is commonly linked to the substantial money it spends on lobbying and political campaigns. A Sunlight Foundation study calculated that the group spent 73 times as much on lobbying the 112th Congress as the Brady Campaign to Prevent Gun Violence, which until recently was the most established gun control organization. Sunlight also found that the NRA spent more than $18.6 million on elections in 2012 – almost 3,200 times as much as the Brady campaign.

But money isn’t the whole story.

Political scientists also emphasize basic differences between the NRA’s base and advocates backing increased gun control. Members of the latter group are less likely to be gun owners themselves, meaning new restrictions often aren’t as tangibly impactful to them.

Furthermore, NRA members are more likely to be single-issue voters, whereas those supporting gun control tend to view the issue as one among many when casting ballots. That means it’s easier to motivate NRA members to contact their representatives in opposition to gun legislation, something the organization encourages through the consistent and stridently-worded communications it sends out.

The votes taken by elected officials often reflect this reality.

“If you’re a member of Congress in a very tight race, and the NRA decides that they’re going to single you out and spend six or seven figures, you suddenly find yourself in a situation you do not want,” said Dave Levinthal, a senior reporter for the Center for Public Integrity, a nonprofit that studies the political influence industry. “You cannot underscore the fear factor enough.”

In explaining her vote against the Manchin-Toomey amendment, Sen. Heidi Heitkamp,D-N.D., said the calls to her office were seven to one against the bill. And a statistical analysis by Nate Silver of the New York Times found that senators up for reelection in 2014 were much less likely to vote for Manchin-Toomey if gun ownership was substantial in their state.

“That’s why 90 percent loses and 10 percent wins,” said Professor Adam Winkler in explaining Manchin-Toomey. Winkler teaches law at UCLA and also studies the politics of gun control. “The 10 percent is more politically active, and they’re obviously more willing to make phone calls and to lobby their elected officials.”

THE POWER OF PERCEPTION

And yet, clear evidence of the NRA’s electoral impact is difficult to demonstrate.

An analysis done by the right-leaning Independence Institute, for example, concluded that in the 1994 and 1996 congressional elections, an endorsement from the NRA could increase “a candidate’s share of the vote by approximately 3% per-10,000 NRA members in the district.” The NRA currently claims 5 million members nationwide.

But other examinations give a different interpretation.  A recent study by David Waldman for the liberal website Think Progress, a publication of the liberal Center for American Progress Action Fund, looked at four electoral cycles from 2004 to 2010. Waldman concluded that “The NRA has virtually no impact on congressional elections.”

Waldman said, for example, that the NRA’s largest Senate campaign expenditures in that period were linked to 10 victories and 12 losses. Regarding endorsements, Waldman argued that “the typical NRA endorsee is a Republican incumbent from a strongly conservative district, strolling to an easy victory,” meaning that the group’s backing is seldom significant.

One could say that Waldman’s electoral data set was unfairly restrictive – that gun control wasn’t a major issue in any of the elections he cited, inherently muting the NRA’s influence. Presented with this criticism, Waldman said the NRA tries to make every election about guns. But more importantly, he also dismissed the significance of the Colorado-based Independence Institute’s conclusions regarding 1994. That year marked a massive Republican political victory that President Clinton himself linked to an NRA-led reaction to the assault weapons ban passed by his administration.

Waldman argued that a confluence of factors meant the GOP was destined for victory regardless of the NRA’s support. He also cited studies attributing Al Gore’s 2000 presidential defeat – routinely connected to the vice president’s record on guns – to “a simple partisan calculation” on behalf of most voters.

The NRA did not respond to requests for comment on Waldman’s study.

Such dueling analyses reflect the difficulty of quantifying the lobby’s impact on any particular election.

“The NRA and the anti-gun groups – they are single voices in what’s a cacophony of outside spending,” Levinthal said, though he acknowledged the gun group’s history of aggressive campaigning. “To hinge individual elections or even an entire national election on the activities of one special interest is incredibly difficult.”

Margorie Hershey, a political science professor at Indiana University in Bloomington, had the same take on the 2012 primary defeat of former Indiana Sen. Dick Lugar, a long-time incumbent with an “F” rating from the NRA.The NRA took credit for Lugar’s loss, but Hershey attributed it more to a general rightward shift of the state’s Republican voters, who wound up selecting tea party candidate Richard Murdoch.

”You can explain the defeat of Richard Lugar in many ways, a number of which have nothing to do with the National Rifle Association,” Hershey said. Even so, Hershey conceded that many pundits believed the group’s impact to be a weighty one.

“That shows that the NRA is just very good at what it’s always been very good at: credit claiming and being taken seriously as a power,” Hershey said.

“The NRA has always worked very hard to punch above their weight in terms of communication and visibility,” Waldman said. “They’re very good at creating the impression that there’s a price to be paid for going against them.”

The result, Waldman said, is that a degree of political influence exists regardless of whether it’s backed up by real electoral muscle.

“You can have a myth of their power that still translates into having a practical impact on what does and doesn’t come out of Congress,” Waldman said. “They’re much more effective as a lobbying organization than they are as an organization that influences elections. But their effectiveness as lobbyists is tied up in people’s belief that they do have that effect on elections.”

Adam Winkler, the UCLA law professor, summarized succinctly. “Power is always perception,” he said.

CHANGES COULD BE UNDER WAY 

But the status quo may face a challenges, sooner rather than later.

“The NRA has largely operated without significant opposition when it comes to their politicking at the electoral level,” Dave Levinthal said. “There just hadn’t been a group that could come close to matching them dollar for dollar when it came to their electioneering power.”

“There’s historically been no rewards and only punishments for opposing the NRA,” said Lee Drutman, a senior fellow with the Sunlight Foundation. “Members of Congress, they always run scared. And everybody knows somebody who lost their reelection because they lost the gun vote.”

But the emergence of new and well-funded gun control groups, such as New York Mayor Michael Bloomberg’s Mayors Against Illegal Guns and Independence USA political action committee, and Gabby Gifford’s Americans for Responsible Solutions, has the potential to alter the established calculus.

Bloomberg has downplayed the NRA’s political power. His Independence USA political action committee spent more than $9.6 million in 2012. In March of this year, the PAC combined with Mayors Against Illegal Guns on a $12 million campaign to push for passage of Manchin-Toomey. Giffords’ group, Americans for Responsible Solutions, raised more than $11 million in the first four months of 2013 alone.

The result could be perceived and real political costs for those who oppose new gun control legislation. Last year, Bloomberg spent $2 million in the race to replace Rep. Jessie Jackson Jr., helping elect the candidate of his choice in a Chicago district.

David Waldman says the activity and spending of these news groups have already shifted the discussion in Washington.

“For years, there was no gun control debate,” Waldman said. “There was the NRA saying, Democrats are coming to take away your guns, and Democrats saying, no, we’re not trying to take away anyone’s guns. And now you actually have a debate with two sides.”