The party slowly made itself unelectable by creating a platform that is too far right and too narrow with no allowance for opposing points of view.
You could even make a case that the 1992 RNC speech by Buchanan started it. Remember how many moderate republicans were completely turned off by that?
I think your right on the money, and it's likely to get worse before it gets better for the GOP since they still seem to be buying into the false idea that they lost in 2006 and 2008 because they weren't conservative enough. They won't win national elections again until they move significantly back toward the center.
