— Not for lack of trying, the issue of gun rights has not played much of a role in the U.S. Senate election in Louisiana this fall.

That could be because issues of any description have loomed small in the campaign, which has centered mainly on, on the one hand, the degree to which incumbent Democrat Mary Landrieu counts Barack Obama, the unpopular Democratic president, as her BFF, and on the other hand, how effectively Landrieu parlays her accumulated influence in the Senate to the benefit of Louisiana.

Or it could be that Landrieu simply doesn’t provide much purchase for her Republican critics — principally the Louisiana spokesman for the Republican National Committee, who has criticized her for her endorsement by the “gun grabber” and former New York Mayor Michael Bloomberg and for consorting (at a shooting range in Maurice) with U.S. Sen. Joe Manchin, D-WVa. Manchin sponsored legislation that Landrieu supported to close the so-called gun-show loophole, which allows firearms purchasers to avoid background checks if they buy their ordnance at a gun show, on Craigslist, in the parking lot of their apartment building or pretty much any place outside of a federally registered gun store.

That position no doubt helped Landrieu earn a “D” grade from the National Rifle Association, despite her opposition to legislation that would ban military-style assault weapons and her support for other measures dear to the NRA.

Her leading Republican challenger, U.S. Rep. Bill Cassidy, of Baton Rouge, earned an A-plus grade from the NRA as well as the group’s endorsement in the Senate campaign.

Her other main Republican opponent, retired Air Force Col. Rob Maness, of Madisonville, was awarded an A based on his response to an NRA questionnaire.

Cassidy, Maness and other gun-rights supporters generally proclaim their fealty to the Second Amendment to the U.S. Constitution, and to a strict construction thereof. Yet, they seem reluctant to press their views to their logical conclusion.

The Second Amendment reads, in its entirety: “A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed.”

Much ink has been spilled over those first phrases, about the well-regulated militia and the security of a free state, and quite a lot expended over “people” (collective or singular?) and even over the meaning of “keep and bear.”

Receiving less attention is the one capitalized word remaining: arms.

That term would seem to cover a vast range of weaponry. “Arms and the man I sing” comes from the first line of the Aeneid, a Latin epic that deals with a time when swords and spears were about as sophisticated as arms got. But then, there are nuclear arms.

One criterion the gun-rights folks apply to rating members of Congress is their position on banning the semiautomatic assault weapons. Presumably, such a ban would affront the Second Amendment.

But fully automatic weapons — machine guns — have effectively been banned since 1934. Nor can you stroll over to your neighborhood Cabela’s (or gun show) and pick up a rocket-propelled grenade launcher or a suitcase nuclear weapon.

Why not? Aren’t those “arms” protected by the Second Amendment?

The obvious response to that line of inquiry is that it’s ridiculous and absurd, which is true.

Seriously — how could the men who drafted the Constitution, brilliant and inspired as they were, have forseen a world of atomic bombs, comprehensive high schools and cineplexes?

But now we’re talking not-so-strict construction of the Constitution.

The core of it is that the debate is not about the Second Amendment — not really. It’s simply about guns, and how you feel about them.

Fair enough. It might lower the temperature of the discussion if we could acknowledge that, however emotionally appealing the alternative, this discussion isn’t about absolutes or about the slippery slope. We’ve already accepted that, and we’re on the slope. We’ve arbitrarily drawn a line: machine guns, RPGs and nuclear weapons are on one side of the line; semiautomatic assault weapons, deer rifles and handguns are on the other.

A proposal to ban semi-automatic assault weapons is simply a suggestion to move the line. It’s not an assault on the Second Amendment.

Don’t hold your breath for agreement on that point.

Gregory Roberts is chief of The Advocate Washington bureau. His email address is groberts@ theadvocate.com. Follow him on Twitter, @GregRobertsDC. For more coverage of government and politics, follow The Advocate Politics Blog at http://blogs.the advocate.com/politicsblog.