The NRAs power doesnt lie solely in campaign money.
There is a lot of discussion about their money, but Ive not seen so much about their main source of power:
The voters they absolutely control.
Politicians who toe the NRA line mostly do not do so because of the money they get, but because of the damage the NRA can do to their re-election prospects. The NRA is assisted in this by the right wing media echo chamber. If they release a statement condemning a pol in an otherwise safe GOP seat for being a gun grabber, that pol is going to get primaried by an NRA endorsed candidate and is going to lose.
Its not the NRAs help that these GOPers fear, its the NRAs wrath. As long as there are districts soaked in AM radio propaganda and Fox News followers, they will not go against the second amendment loons. Until we have candidates, red or blue, winning in these districts, voted in by a majority who no longer buy the NRAs bullshit, the NRA will continue to call the shots on gun laws.