One of the drumbeats coming out of the biennial race to represent Minnesota's 8th Congressional District refers to Democratic incumbent Rick Nolan as "F-rated by the NRA."

Despite the 72-year-old congressman being a known hunter and outdoorsman, challenger Stewart Mills has conjured the National Rifle Association's F-rating of his opponent at every turn - often in his opening remarks to crowds.

In an October interview with the News Tribune, Mills was asked about his use of Nolan's F-rating from the NRA as a pillar in the 44-year-old Republican's three-legged campaign platform - one that also includes overturning the Affordable Care Act and reducing federal oversight and regulation of businesses large and small.

"Time and time again Congressman Nolan says we need stricter controls on guns and who can have them," Mills said, before finishing his thought by citing a list of recent mass shootings or gun attacks on innocent civilians and schoolchildren. "But the proposals that Congressman Nolan put forward would not have saved a single life in Orlando or San Bernadino or Chattanooga."

But even taking into account his earlier terms in Congress from 1975-81, Nolan hasn't authored a legislative gun control measure - ever - among the 188 bills he's put forward.

Understanding Nolan's F-rating with the NRA, then, becomes a deeper exercise and one that would seem to skew political despite the organization's insistence that it is a nonpartisan entity.

In a phone interview last week from the campaign trail, Nolan said he pays scant attention to the rating and that he hardly ever hears about it from corners other than the Mills campaign. Nolan added that he is comfortable with his defense of the Second Amendment right to keep and bear arms, he said, "for hunting, recreation and personal protection."

"They've become more rigid in recent years," Nolan said of the NRA. "But we've always had a wide variety of gun safety measures. All my life it's been three shells while shooting ducks. When I take my grandkids out deer hunting they've had to go through gun safety to get a license."

When asked if the harsh rating of Nolan rings hollow - given his association with gun sports and the other grades available in the rating system - NRA spokeswoman Catherine Mortensen bristled, calling Nolan "a poser" and saying the ratings were a useful tool for voters.

"Our members and supporters know what an F-rating means and it does not ring hollow to them," she said. "If you care about the Second Amendment and if that motivates you and informs your vote you will know what an F-rating means; it's crystal clear."

According to the NRA's definitions of its grades, an F-rating equates to "a true enemy of gun owners' rights," and Mortensen said Nolan's sporting history means little compared to his voting record, past statements and participation in things such as June's demonstration on the floor of the U.S. House of Representatives, where Democratic legislators staged a sit-in for more than a day in an effort to bring about a vote on "no fly/no buy" legislation. The demonstration followed in the wake of the Orlando nightclub shooting massacre that killed 49 people and injured dozens more; Nolan joined a swath of legislators demanding a vote that would have placed restrictions on gun sales to terror suspects already prohibited from flying on an airplane. The measure never passed.

"If you hunt on weekends or own a gun, that's great," Mortensen said, "but that's not what we base our grade on. 'How do you vote?' is the bottom line."

Nolan said he would continue to support future efforts at no fly/no buy legislation.

"Why give someone who has sworn allegiance to kill Americans access to guns and ammunition, whereas you wouldn't with some guy found guilty of writing bad checks?" Nolan said, referencing a convicted felon's prohibition from purchasing or possessing firearms. "It doesn't make a lot of sense - which is why not many people seem worked up about my F-rating."

State Rep. Jason Metsa is busy with his own political campaign to represent the Iron Range's District 6B. Like Nolan, Metsa is a DFL incumbent. Unlike Nolan, Metsa is A-rated by the NRA. But it's a grade that means so little to him, "I quit filling out their endorsement questionnaire," Metsa said.

Metsa described Nolan as a good friend and explained that the lack of stock he places in the NRA grades is related to the organization's treatment of Nolan.

"Just to blanket him and say Rick Nolan wants to take your guns away is ludicrous," Metsa said. "I know what he feels about guns; we've talked in-depth. There's no one you would rather have in the hunting shack with you or in the duck blind than Rick Nolan. He's passionate about the outdoors."

Metsa added that he believes Nolan is being penalized for positions he took during his first terms in Congress, beginning in the 1970s, when his positions on guns aligned more closely with an NRA that was more sporting-oriented and less strident in its defense of all things related to the Second Amendment.

"What an irony?" Nolan said. "Positions they (once) supported now give you an F-rating in their system."

The NRA's Mortensen said it's not the organization that has changed as much as the legislators themselves.

"We used to have a lot more Democrats who were very strong supporters and had very good grades with the NRA," she said. "But in recent years they have purged a lot of those more centrist Dems who were more likely to be strong Second Amendment supporters. It's nothing that we could control. It's an unfortunate development - one of our greatest strengths is that we are nonpartisan."

Mills' candidacy has been supported by the NRA with an A-rating - a qualified one, since he has no voting record as a legislator. But as the scion of the family that built Mills Fleet Farm into one of the Midwest's busiest gun sellers, his appeal to the NRA is obvious. Since his bid for public office first began in 2013, Mills has stood on a platform that would protect the Second Amendment from any and all legislation aimed at gun control.

"When we're taking a look at mass acts of terror, if you're looking at guns you're looking in the wrong direction," Mills said to the News Tribune this month. "... What we really have to go after is security."

A proponent of the "good-guy-with-a-gun" argument, Mills pointed to the recent attack at a St. Cloud mall, where an off-duty police officer used a gun to stop a knife-wielding assailant.

"He was an armed citizen that was carrying a gun and he was able to stop an attack," Mills said. "We have tens of millions of guns in the U.S., so that genie is out of the bottle. Even if you say, 'We're going to stop it from here on out,' and start banning certain types of guns, they're still on the streets.

"What we have to do is make sure our schools are safe and the armed citizen can fully participate in their Second Amendment rights in the community."

A Mills plan would have both incoming and retired police officers armed and operating in plain clothes in schools. New officers would gain experience and build resumes, he said, while retired officers would provide expertise in protecting schools.

Meanwhile, Nolan and Metsa say the vast majority of voters they talk to have no problem with no fly/no buy legislation. When discussing future directions for gun control, Nolan brought up that private sales online and at gun shows don't require background checks - even for people with felony backgrounds or other "people adjudicated to be criminally or mentally violent," he said.

"You can't buy guns through normal channels without a background check," Nolan said. "But a lot of guns are purchased at gun shows and online and to suggest that anybody go buy at a gun show doesn't make any sense to me. The NRA doesn't see it that way, so I get an F."