To understand the importance of this factor, Obama and gun control advocates have to grapple with the fact that Mitt Romney carried 228 out of 435 House districts (52.4 percent) despite losing the national popular vote to Obama by 4 points. According to an analysis by FairVote, the median House district (the 218th) is one that leans 52 percent Republican. Cook Political Report analysis found that of the 234 Republicans elected to the 435-seat U.S. House in November, fully 219 came from districts that were carried by Mitt Romney. That means that these Republicans don't need to worry much about challenges from the left or accommodating the president over the next two years. It also means that Democrats will have a very steep uphill climb to retake the House in 2014, since their candidates would have to run well ahead of their presidential nominee in at least a dozen Republican-leaning districts.

Just like our recent presidential election was settled in only a handful of battleground states, control of the U.S. House of Representatives comes down to only about 35 districts -- fewer than 10 percent of the 435 districts -- every two years. That gives overwhelming power to undecided voters who live in these swing districts, many of which are rural and conservative-leaning. This set-up also gives enormous power to the NRA, because many NRA members live in these rural swing districts.

So the Democrats and Obama know that the NRA doesn't have clout because it has lots of money -- it spent $18 million in congressional elections in 2012 -- but the contrary. The NRA has money because it has clout. And it has clout because it has a lot of votes in key battleground House districts and battleground states voting for president and U.S. senators.

Back in 2000, Republican strategist and NRA board member Grover Norquist summed it up nicely, saying, "The question is intensity versus preference. You can always get a certain percentage to say they are in favor of some gun controls. But are they going to vote on their 'control' position?" Though many voters back gun control, says Norquist, their support doesn't really motivate them when they go to the polls. "But for that 4-5 percent who care about guns, they will vote on this."

Things have hardly changed since Norquist made those comments. The NRA's job is made easier because it can target its resources at the three dozen swing districts like a military strategist dividing quadrants on a battlefield. That allows a small number of NRA voters to form a potent single-issue voting bloc, since a change in 5 percent of the vote in any swing district can make all the difference. The NRA has power not so much because of its deep pockets but because of the fundamental design of our geographic-based political map in which representatives are elected in single-seat, winner-take-all districts.