Which lawmakers got the most NRA money? In the past 15 years, the NRA has spent more than $132 million on political ads.

 -- Last week's shooting at a Parkland, Fla., high school that left 17 dead and 14 wounded has once again brought the debate over gun control to the forefront. This time, the school's students are taking the lead in demanding change at both the local level and in Washington.

Critics, however, argue that pro-gun campaign money has more influence in the gun policy debate than victims of gun violence.

The National Rifle Association continues to be a huge force in American politics. It's made more than $11 million in direct contributions to federal lawmakers and candidates over the past 20 years. In 2017, the group's lobbying expenditures included $5 million spent pushing Second Amendment rights.

But the NRA’s real power shows up in independent expenditures. It can raise and spend unlimited amounts of money supporting or opposing candidates - as long as it doesn't coordinate with the candidates.

During just the 2016 election cycle, the NRA spent $54 million in the presidential and congressional races, nearly $20 million of which went to attacking Democrat Hillary Clinton and more than $11 million to support Republican Donald Trump. In 2008 and 2012, the group had spent $18 million opposing Democrat Barack Obama and $10 million supporting Republicans John McCain and Mitt Romney.

A NRA spokesperson said the group spends money in elections on behalf of its five million members across America to defend their constitutional right to own guns.

In the past 15 years, the pro-gun group has spent a total of more than $132 million on ads supporting or opposing presidential or congressional candidates.

Here are the three U.S. senators and House members who have benefited the most from the NRA’s ad buys, according to Federal Election Commission records:

SENATE

Sen. Richard Burr: $6.9 million

In 2016, the NRA was determined to keep North Carolina Republican Sen. Richard Burr’s seat. The group spent $5.6 million on ads attacking his Democratic challenger, Deborah Ross. Over the years, the group has spent $1.4 million on ads supporting Burr and donated $40,150 to his House and Senate campaign committees.

Sen. Roy Blunt: $4.5 million

Sen. Roy Blunt, R-Mo., has long been one of the biggest beneficiaries of NRA money. Not only has the group donated $56,500 to Blunt’s campaign committee over the years, the group has also spent $1.4 million bankrolling ads supporting him. The NRA also spent $2.5 million in 2016 opposing Democrat Jason Kander’s bid against the Missouri Republican.

Sen. Thom Tillis: $4.4 million

The NRA was one of many outside groups that helped unseat North Carolina's Democratic incumbent senator, Kay Hagan, and elect Republican Sen. Thom Tilllis in 2014. The NRA spent $2.45 million against Hagan and nearly $2 million in support of Tillis.

HOUSE

Rep. French Hill: $1.1 million

The NRA was one of the biggest spenders in a competitive Arkansas House race in 2014. The group spent more than half a million dollars supporting Republican French Hill and another half million attacking Democrat Patrick Hays.

Rep. Ken Buck: $829,377

In 2010, the NRA spent nearly $830,000 in an unsuccessful effort to replace Democratic incumbent Michael Bennet with Republican Ken Buck in Colorado. Buck, however, was able to win the seat only after Bennet left office to run for the Senate in 2012. The NRA didn’t get involved in the 2014 race, but Buck was backed by another pro-gun group called Gun Owners of America.

Rep. David Young: $697,778

The NRA helped elect Republican David Young in an open House race in Iowa in 2014 by spending nearly $700,000 on ads in support of Young and against Democratic opponent Staci Appel.