I second Cosmoline's succinct strategy outline, with regard to supporting reasonable candidates and incumbents and trying to unseat unreasonable incumbents. In the western/mountain states, in general, his point about "of either party" applies and is important (to the poster up-thread from MT, your two senators, I think embody this pattern - western/mountain Dems have long been reasonable on "gun control" issues).
The "either party" approach, sadly, is hardly applicable elsewhere any more. Certainly not on the coasts (outside the SE). Which is not to say the GOP types are "reliable" in any sense - on the contrary. Just that while many GOP types these days will easily go along with further shredding of the constitution, evisceration of the rule of law, and indefensible liberty-killing and ineffective "solutions" to insoluble problems, they are far less likely to INITIATE such deplorable actions (esp. in the "gun control" arena). Take CA. A ridiculously mismanaged and mis-governed place, insolvent, in many respects lawless, firmly in the grip of pseudo-science, racism, and greed (public sector greed). But it's hard to imagine many of the dozens of absurd and unconstitutional "gun control" laws being on the books if there were a GOP majority in either house for the last two decades. The GOP is far less reliable than it was - the Dems (with exceptions) are unrecognizable (and not just on "gun control"). So I'd add that important caveat to Cosmoline's sound observation.
CA might (I said might) have a rather odd situation that may mitigate the damage (for now). Gov. Brown, certainly an interesting character among contemporary political figures, has always shown a striking appreciation for both the constitutional and practical problems of "gun control" ideas. As attorney general he filed a supportive brief on a key SCOTUS 2nd Amendment case (can't recall if Heller or MacDonald) - that had to cause a stir among many of his very dim and dangerous supporters. A friend tells me he also made a public comment in December not long after the CT events, something to the effect that "CA does not need any more gun control laws". (I have not documented that).
The last few years have removed nearly 100% of my confidence that I understood and could forecast (to some degree) the political behavior of the country - after decades spent inside the Beltway actually gaining my understanding first-hand (including years working in the Senate). Even before 2008, things started to seem surreal. Of course 2008 and after have offered one jaw-dropping, pinch-myself-am-I-really-seeing-this moment after another. Now I don't recognize most of the country, and remain in a state of shock and disgust even years into the nightmare.
I speculated a few weeks back to friends that the last remaining "third rail" of US politics might just be "gun control". So far, on a national level, it seems to be. For now.