The largest miscalculation in their 90%, is the large percentage of pro gun law supporters who trust the government even less than they do their own ideals.
I believe for them to pass any such background check or anti-gun law they will have to do so without the support of the majority of Americans.
Even with that being said i have little faith that the of support from pro-gun people against such law, Splashed across national headlines, ( we know that will never happen even if proven) would neither slow their effort nor change their vote.
Adding to that, should it happen I doubt very seriously the supporters of the second amendment can or will mount a large enough rebuttal to render an appeal process as long as the passage of the new law doesn't affect the majority of gun owners.
I would submit the many laws that have been passed without the support of the majority of the American people and the strongest of which are used for little more than a smoke screen proposed as a true stance on belief or values in trade for the almighty vote.
Just as a note for reference i believe the patient were testing waters to see if the water is warm enough yet. They will be back.