New York, NY —

Mayor Michael Bloomberg is a known gun control advocate, and has built a national platform to stem the flow of illegal guns into cities and towns. The group he co-founded in 2006, Mayors Against Illegal Guns, has grown from 15 to 526 mayors. Its success has raised the ire of gun rights groups, most notably the National Rifle Association.

The showdown between the NRA and Mayors Against Illegal Guns is playing out across the country: in blogs, on the editorial pages of newspapers, and at countless gun clubs. At the Ridge and Valley Rod and Gun Club, in Coopersburg, Penn., Rick Hubrich is getting a little target practice. He says he loves animals and never hunts, but he does think gun owners help maintain the law. Today he's brought his tricked-out, AR-15 semi-automatic to the outdoor range, as well as a pistol fitted with a silencer.

"It's disgusting that any one man can cause so much turmoil," Hubrich says.

Hubrich sees Mayor Bloomberg as the poster boy for gun control.

"It's disgusting because he never speaks the truth -- he always twists a little bit," Hubrich says. "He's good at it. I'll give him credit. He's good at that. Once the more educated mayors and sheriffs see what he's doing, they back out. Because they know it's a lie."

In fact, 15 of Pennsylvania's mayors have quit Mayors Against Illegal Guns since the NRA began a campaign in September. That's out of about 150 mayors who are part of the coalition, the most of any state.

The NRA's anti-Bloomberg campaign followed its failure in passing the Thune amendment in Congress. That measure would have let gun owners cross state borders with their weapons, even if they received their licenses in states with weak gun laws. The mayors group opposed the amendment, and in the end they won.

For some members of the gun club, like Bob Hermida, the growth of the mayors group shouldn't be seen in isolation, but as part of the White House agenda: "Obama has the support on the Hill because he listened to his constituents, saying hey, calm down. But meanwhile, he's whispering in Bloomberg's ear: push the issue."

One person who got the message from local gunowners is Walter Niedermeyer, mayor of Slatington, Pennsylvania, who could be found at his town's police station. Some of the mayor's voters had been getting letters from the NRA, noting Niedermeyer's membership in Mayors Against Illegal Guns, or what it calls the Bloomberg coalition. Mayor Niedermeyer felt he had no choice but to quit.

"They sent me these letters, they called me up, asked me please get off it, so I figured, these are the people that vote, these are the people I work with, these are the people I support too, so I'll do what they want me to do," he says.

But after the recent elections, it's gun control advocates who say they came out ahead. One group, Ceasefire Pennsylvania, says all 12 of the candidates it endorsed won re-election, despite opposition from the NRA. By contrast, gun rights groups couldn't name any members of Mayors Against Illegal Guns in Pennsylvania who lost re-election.

The issue is heightened here because Mayor Bloomberg blames Pennsylvania for a large flow of of illegal guns into New York City -- more than any other state but Virginia. But the NRA has gone after mayors in other states, too.

Bill Barnett is the mayor of Naples, Fla. - and a gun owner - and says he received nearly a hundred emails and angry phone calls from people who'd gotten the NRA mailer. He says the mailer distorts the coalition's goals: "It amazed me that someone would read the postcard and it was almost like Pavlov's dogs, that they would say, if they said this is the truth, then this must be the truth."

And Barnett says he's staying in the mayors coalition.

Back in New York, Mayor Bloomberg sits in a room after a press conference, quietly conferring with the architect of his gun strategy, John Feinblatt. Bloomberg has spent nearly $3 million of his own money on Mayors Against Illegal Guns. And he seems unfazed by the defections from the group. The mayors who've left, he says, are mostly from small towns, where gun owners have a major voice. And for the 60 or so who've left since the NRA began its campaign, another 150 have joined.

"The growth is as good as its ever been," Bloomberg says, "and I think you're going to see once you get critical mass a lot of mayors will join. And they're going to say to the NRA, come on, this is craziness."

The mayor says he doesn't want more gun control laws so much as better enforcement at the federal level. He also claims the high ground, based on New York's ever-plummeting crime figures.

"In New York City, you certainly don't need guns to protect yourself," he says. "And I would argue that fewer guns in the hands of criminals, in the hands of kids, would reduce the crime rate elsewhere as well. The NRA doesn't buy it, though, and aside from its mailers, has been trying to alert gun owners on TV, and online."

NRA spokesperson Rachel Parsons counters that, "Mayor Bloomberg and his group Mayors Against Illegal Guns represent a serious threat to our rights because of the attention the media will give them and the resources a billionaire like Bloomberg has at his disposal."

Parsons says many of those who join the coalition don't realize its true ambitions. She says the group's push to close the gun show loophole and loosen access to gun trace data are the first steps down a slippery slope. "They have lobbied Congress time after time for more restrictions and more restrictive gun control legislation and we think that if their constituents do not agree with that then they are not representing those who put them in office."

But for gun control advocates, the mayors coalition has become a useful, and well-funded ally. Paul Helmke is the president of the Brady Campaign to Prevent Gun Violence. He says mayors deal directly with victims of crime and police departments, so they have not just the bully pulpit, but moral authority as well.

"I really feel it's been one of the most significant things to help affect the debate on gun violence prevention in a number of years," Helmke says.

Others, however, say it's too early to make a call. John Bruce is a political scientist at the University of Mississippi. He says the mayors group has begun to influence the debate, and that the NRA has reason to be nervous. But in terms of actual policy, he says the group's impact is still hypothetical. And given the fact that Democrats in Congress aren't leaping to take on the gun lobby, he doesn't expect any real change anytime soon. "They got through all the school shootings, right, Pearl, Mississippi, Jonesboro, Arkansas, Columbine, with no real changes in the law. No real changes in access. So what the NRA philosophy has been is essentially to build a firewall. A firewall that has enormous political consequences for breaking."

But Bruce says the mayors coalition has tremendous potential, and that he intends to keep watching what it does, and how the gun lobby responds.

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