All of these changes were driven by facts on the ground. To listen to Democrats, Republicans support gun rights because the NRA tells them to. In reality, Republicans support gun rights because their voters tell them to, just as Democratic voters tell their representatives the opposite.
But guns and immigration are not simply drivers of polarization, they are examples of its power. Politics has become a lifestyle, part of the “Big Sort” driving so much in our culture. That’s why the NRA’s marketing these days has so little to do with gun policy and so much to do with smash-mouth cultural resentments.
These days, if you’re a Democrat, you’re likely to be a down-the-line Democrat on a host of unrelated issues. Same if you’re a Republican. Like our representatives, many of us won’t buck party orthodoxy on any matter of importance.