Being a one issue voter is a very narrow minded way to live
To me, there's usually one issue that is more important to me than others. That doesn't mean I am a 1 issue voter guy, though.
However, if I feel that that one issue is so important as to not be ignored, then that's what I go on. Case in point, in the 2006 mod terms, terrorism was my biggest issue and I cast my vote for those would agree with me.
I am not sure if that all makes sense, it's difficult to put into words sometimes.
In a superficial sense it might seem narrow minded, but I'm to a large extent in agreement with the original poster. The fundamental issue political issue of all time is whether government should define its own limits and have power over us, or whether government should be limited in size and answerable to us. Since the 2nd Amendment, which provides our God-given right to keep and bear arms with unlimited legal strength in the phrase "shall not be infringed", is the guardian of the power to decide whether we rule or are ruled, it's a good single issue to use as a touchstone. Any candidate who wants the citizenry capable of resisting unwarranted government decrees has the right fundamental values, while any candidate who wants to make sure that government can compel obedience is (like Obama and Pelosi) an enemy of freedom.