I want to respectfully add that there are some wrong-headed ideas here. Standing on the sidelines is entirely unproductive in a democracy. With just a little persistence, a little hard work, and if you like, a little money one person or a few people can pretty much ensure that the local branch of one of the two political parties listens to them and adopts their idea in one form or another. That is because the percentage of people who really show up and participate in democracy is very small. And since we have a two party system, and since my issue is fighting gun control, I find it much easier to work for and influence Republican campaigns than I would Democrat campaigns. I should add that it's true that all politics are local politics.
Sure, there are many issues where I don't see eye to eye with any particular campaign, and I am not aligned with general Republican platforms on many issues. But starting my own party would not help me fight gun control at all. Moreover, trying to have the party adopt my ideas on several issues instead of just one issue would dilute any good that might come from my work on campaigns.
Most guys I hunt with express some of the same ideas I have on some social issues but arguing those issues with their wives and their preachers would get them nowhere. Pragmatically, if the Republicans continue to honestly push back against gun control, including appointing judges who support the Constitution, then I am not going to argue with them very much about the issues that are not so important to me but are hot-button issues for other Republicans. Given the close vote of the Heller decision the appointment of judges is very important to my issue.
So in a two-party system we have just a few choices it seems to me, and one of them is to be involved. If you are involved then you will see that people who believe in the 2nd Amendment tend to overwhelmingly be Republican.