Correction: An earlier version of this story incorrectly reported that Sen. Pat Toomey, R-Pa., wasn’t planning to co-sponsor legislation seeking to expand background checks for gun purchases if reintroduced. While Toomey noted that it was “unlikely” another attempt to pass the measure would succeed in Congress, he said he would be a co-sponsor of such a bill if it were to be reintroduced.

A National Rifle Association billboard in Hendersonville, Tenn., attacking then-Tennessee House Republican Caucus Chairwoman Debra Maggart in July 2012. (Erik Schelzig/AP)

As a lifetime member of the National Rifle Association with an “A+” rating for her voting record in the Tennessee House of Representatives, Debra Maggart never imagined that her political career would end this way.

Maggart, who chaired the Republican caucus, killed an NRA-backed bill that would have permitted Tennesseans to keep firearms in their parked vehicles wherever they went — work, school or the neighborhood bar.

Months later, Maggart was stunned to see NRA-sponsored ads on billboards in her district. Her face was next to a picture of President Obama. The ads proclaimed: “Sure, Rep. Debra Maggart Says She Supports Your Gun Rights. Of Course, He Says the Same Thing.”

The NRA threw its support behind a newcomer in the Republican primary. By summer’s end, the woman who had been one of Tennessee’s most powerful Republicans and ardent supporters of gun rights was done in by hardball tactics.

“As a pro-Second Amendment person and a life member of the NRA, I was just shocked they did this to me,” Maggart said in an interview. “They did this to send a message: ‘If you don’t do what we want, we will annihilate you.’ ”

The message has not been lost on lawmakers across the nation, including those in the U.S. Senate, where a proposal to expand background checks for gun purchases died April 17 in the face of the NRA’s staunch opposition.

For longtime NRA members, the Senate vote was not surprising. The group has turned the debate over gun control into a clarion call for constitutional rights. Any perceived assault on the Second Amendment is met with a withering counterattack. Even conservative lawmakers who cross the NRA are labeled as traitors. The NRA has been so effective over the years that gun-control groups are now trying to adopt some of the same tactics.

Well-organized NRA members and affiliated groups of gun owners hold rallies and pour resources into political campaigns. They flood local and national legislative offices with e-mails and phone calls. They make unannounced visits to the offices of lawmakers. The NRA’s lobbying arm posts myriad “Alerts,” calling on millions of members across the country to rise up at a moment’s notice.

It’s more about organizing muscle and less about political money.

A spokesman for the NRA did not return calls requesting comment.

“The NRA knows how to play very effective hardball,” said Richard Feldman, a former NRA lobbyist who wrote the book “Ricochet,” an inside account of gun politics and tactics. “They have turned this into a symbolic issue. It’s no longer about guns. It’s about freedom and responsibility and liberty.”

After the Sandy Hook Elementary School shootings in Newtown, Conn., in December, Sen. Mark Begich (D-Alaska) said he could sense a “sea change” in gun politics. He issued a public pledge: He would not “shy away” from challenging the NRA, which has great influence in his state.

That was before Begich was overwhelmed by phone calls and e-mails from NRA members and other gun rights activists. They warned him against voting for expanded background checks, to stop violating “our gun rights,” and to break with the Democratic Party or face the consequences in the next election.

Begich was one of four Democrats from states with strong NRA membership to turn his back on his party and the legislation.

‘One strike and you’re out’

The NRA’s tough tactics have a long history. In 1994, after President Bill Clinton pushed criminal background checks and a 10-year ban on assault-style weapons through Congress, the NRA organized a grass-roots uprising.

The midterm elections that year were a bloodbath for Democrats who opposed the NRA, and Republicans took control of the House of Representatives for the first time in 40 years.

Some of the most influential members of the Democratic Party lost their seats that night, including House Speaker Thomas S. Foley (Wash.) and House Judiciary Chairman Jack Brooks (Tex.).

“The NRA had a great night,” Clinton would write in his autobiography. “They beat both Speaker Tom Foley and Jack Brooks, two of the ablest members of Congress, who had warned me this would happen. . . . The NRA was an unforgiving master: one strike and you’re out.”

George “Buddy” Darden was one of the 54 House Democrats to lose his job that night. For nearly 10 years, he had represented a district that included suburban Atlanta and swaths of rural Georgia, an increasingly conservative district with an well-organized contingent of NRA members.

Darden opposed the ban on assault-style weapons, but he wound up voting for the bill that contained the 10-year prohibition. The NRA leadership was infuriated. It recruited conservative religious groups, along with like-minded city council members and county commissioners, to attack Darden and support Republican challenger Robert L. Barr Jr., who used a local gun shop as a campaign base.

Barr won with more than 52 percent of the vote.

Looking back, Darden said numerous factors played into his loss. Although he refused to give the NRA full credit, he acknowledged that the group influenced the outcome of that race.

“The NRA is a take-no-prisoners organization. There is no margin of error with them,” Darden said in an interview. “I knew their position, and I can’t complain. I just felt that the Second Amendment, just like any other amendment, is not absolute.”

Feldman, the former NRA lobbyist, remembers the Darden-Barr race well. At the time, he was chief executive of the American Shooting Sports Council, a trade association for the firearms industry.

“He voted for the final package that included the assault weapons ban, and the day after he did that, there were lines around the corner of the gun store of people supporting Bob Barr,” Feldman recalled. “The NRA supported Barr. We supported Barr. You do what you do in a democracy.

“You support your friends, and you oppose your enemies.”

‘I couldn’t believe it’

Debra Maggart has been around firearms all her life. Her family owned Carter Hardware in Nashville, which sold rifles, shotguns and handguns. She got her hunter’s license, joined a local gun club and went to the Tennessee House in 2004 as a pro-gun lawmaker.

“You can’t get more pro-Second Amendment than me,” she said.

Last year, Maggart said, the NRA drafted a bill to permit concealed weapons to be kept in locked vehicles no matter where they were parked. She said business and property owners objected, arguing that they could be liable for gunfire on their properties. Maggart tabled the bill in April 2012.

In early July, she started to receive frantic phone calls from her friends.

“Have you seen the billboards?” they asked.

“I went out and looked, and I couldn’t believe it,” she said. “The billboards said I was just like Obama, and where I’m from, that’s deadly.”

The billboard ads were followed by radio spots, newspaper ads and fliers mailed to homes in her district: “Maggart and Obama: We Can’t Trust Either With Our Rights.”

On YouTube, Chris Cox, chief of lobbying for the NRA, went after Maggart.

“We’ve put up ads and billboards comparing Debra Maggart to Barack Obama,” Cox said. “That’s because, while both say they support our Second Amendment rights, they both worked against our freedoms behind closed doors.”

Maggart estimated that the NRA and other gun groups spent $155,000 on the race. She said all she could do was watch her polling numbers fall. She ended up losing the Republican primary by 16 percentage points to a candidate handpicked by the NRA, Courtney Rogers, a retired Air Force lieutenant colonel who had no political experience.

“They will lie about you. They will use intimidation tactics. They will use bullying tactics, and because of that, people are afraid,” Maggart said.

“Why wouldn’t you be afraid?’”

Ayotte in the middle

After watching the NRA’s successes on Capitol Hill and in statehouses across the nation, gun-control groups are starting to employ some of the same tactics.

Nowhere has that been more apparent than in New Hampshire, where Republican Sen. Kelly Ayotte finds herself caught between two powerful forces: the NRA and Mayors Against Illegal Guns.

Ayotte was the only senator from a Northeastern state to side with the NRA.

Since the vote, the NRA and the National Shooting Sports Foundation, a firearms industry trade group, have been running radio spots in New Hampshire that praise Ayotte for her stance.

“Kelly Ayotte is not just a senator, she’s also a mom who cares about protecting our kids,” the announcer says. “Kelly had the courage to oppose misguided gun-control laws that would not have prevented Sandy Hook.”

Gun-control groups are hitting back. The mayors group, organized by New York Mayor Michael Bloomberg (I), has tapped a deep reservoir of phone and ­e-mail lists to mobilize opposition to Ayotte. Protesters have trailed Ayotte to events in New Hampshire, demanding that she explain her vote.

On April 30, the daughter of the slain Sandy Hook principal confronted Ayotte at a crowded town hall meeting in Warren, N.H.

The scene was reminiscent of the way the NRA had taken over town hall meetings.

“A fair amount of what we’re doing in New Hampshire is right out of the NRA playbook,” said Arkadi Gerney, who was a special adviser to the mayors group before joining the Center for American Progress as a senior fellow. He and others are helping to coordinate the anti-Ayotte campaign in New Hampshire.

One of the lessons learned: Every vote in every city, county and state cannot be taken for granted.

“We’re on the ground, moving people on our side,” Gerney said. “You have to have people show up at the events, send letters and make the phone calls.

“It’s not enough to have 99 percent of the people agree with you.”

Toomey’s quandary

Until recently, Sen. Patrick J. Toomey (R-Pa.) was considered a friend of the NRA’s in the halls of Congress and in the Lehigh Valley of Pennsylvania, a state that boasts one of the highest concentrations of NRA members. The NRA had given Toomey an “A” rating for his dependable voting record and, in 2011, invited him to speak at its annual Celebration of American Values Leadership Forum.

That was before Toomey this spring joined Sens. Joe Manchin III (D-W.Va.) and Charles E. Schumer (D-N.Y.) to introduce legislation to expand federal background checks. Even though the measure failed, gun rights activists say Toomey crossed the “line in the sand” drawn by the NRA.

William A. Bachenberg, an NRA national board member who directs the organization’s efforts in eastern Pennsylvania, said Toomey undercut his credibility in the gun rights community. Bachenberg said many of Toomey’s supporters see the background-check proposal as a purely political move to help him win reelection in 2016 in a state where Democrats outnumber Republicans by nearly 1 million voters.

“I will not support him,” declared Bachenberg, who owns a skeet-shooting range in the Lehigh Valley and said he was not speaking on behalf of the NRA. “A lot of shooters have been coming to the range, and they feel betrayed. When you talk about constitutional rights and an issue that is this dear to us, this is very frustrating.”

John F. Brinson has been a friend of Toomey’s for more than 20 years. But as a co-chairman of the Eastern Pennsylvania Firearms Coalition, Brinson said he sees trouble on the horizon for the senator.

“I will support Pat, but a lot of people won’t. They are so angry,” Brinson said. “I have a right to keep and bear arms, period. And this is the kind of thing that sets off gun owners and makes us crazy. This is not gun control, this is people control, and they are treating us like children.”

Before the proposal was defeated, Toomey said he knew that the NRA would be angry.

“My approach is to do the right thing and let the chips fall where they may,” he said in an interview. ”I don’t know what the political implications will be. I don’t think anyone does. “

Manchin has said he plans to revive the background-check legislation. Toomey noted that it was “unlikely” another attempt to pass the measure would succeed in Congress, but he said he would be a co-sponsor of such a bill if it were to be reintroduced.

Magda Jean-Louis contributed to this report.