The NRA was not a large and powerful or sophisticated lobbying and political organization until after the 1968 gun control act.
Prior to that they were primarily a hunting and marksmanship organization.
In 1968, after the hysteria of the assassinations of President Kennedy, Martin Luther King and then Bobby Kennedy the country and the congress and president were united in desiring gun control. Gallup polls in that decade showed that the majority of people favored a handgun ban. The NRA membership itself was divided between hunters and target shooters who also supported gun control and those that did not.
Many states already had long standing gun control in the form of bans on concealed carry and open carry - many a legacy of Jim Crow.
Since that time after many internal battles at the NRA that supported a harder core stand against gun control and years of developing support through education, scholarship on the second amendment, and developing a larger and more powerful lobbying and political presence the NRA has played a major role in turning around the direction of state and federal governments, the courts and public opinion at large.
The NRA supported the gun control act of 1984 which repealed many of the worst provisions of the 1968 gun control act. However the poison pill amendment that banned all new machine guns was put in at the last minute and the NRA had to choose between having Reagan sign it or having him veto it. They chose to ask him to sign it in the stated belief that they could get the ban repealed. Which has not been the case.
The NRA did not support the Heller case initially as they were afraid that a loss would be catastrophic, a ruling that the 2nd amendment did not protect an individual right. So they did work to derail it. They have since been aggressive in pursuing cases in court.
The NRA has been instrumental in helping to foster many state level gun rights organizations that together have helped to establish the right to carry in state after state - today 38 states have a shall issue right to carry and 3 or is it four have constitutional carry and there will be more. Current court cases are moving forward from the SAF and the NRA to codify the right to carry as part of the 2nd amendment constitutional right.
In Maryland a republican appointed district judge ruled that there is a constitutionally protected right to carry outside the home - in Illinois a democratic appointed judge ruled there was no right.
Hopefully the USSC will decide that there is a right to carry outside the home found in the 2nd amendment. But that depends on the court being willing to do so, and on there being five justices who in Heller and McDonald supported a real 2nd amendment. None of those five were appointed by a Democrat - the oldest of the five is Kennedy at 77 yrs old. Younger justices who will serve for life are democratic appointees who do not support a real or meaningful interpretation of the 2nd amendment. A conservative republican president after 2012 could help to cement a pro-2nd majority whereas a liberal democratic president could very well appoint justices that overturn Heller and or more likely water it down to meaninglessness by subsequent decisions that effectively gut it.
There are other routes to marginalize the RKBA - agencies like the EPA and such have the power - given presidential directive and a lack of strong congressional support of severely damaging the practical RKBA.
Perhaps the NRA is sometimes a little over the top on their rhetoric about the threats to the RKBA - but not by much in my opinion. Our RKBA will only exist and continue if we fight to support it. The minute we stop, we will start to lose it. Maybe not all at once, but certainly a piece at a time, and those pieces will add up. The NRA is far from perfect - but the members do get a say and a vote. And the NRA is the 800 lb gorilla in the room, the only one, when it comes to national gun control.
Due in large part to the NRA we would not have the freedoms we have today. Without the NRA it would be bleak and today we would be much more like England or Australia.