I think you’re correct that mainstream leaders of the parties try not to talk about each other in that way and mostly succeed. But I absolutely do know family members and friends treat it with that level of zeal.
replyI think that's true of just darn near everything. People are tribal and tend to get uncomfortable when people around them change:
reply* Their political parties
* Their religions
* Their diets (meat => vegan, or vice versa)
* Their music
* Their computer OS
None of those compare to cult shunning, which is more systematic and absolute. I mentioned in another comment that my parents were sad when I stopped going to church. That's got nothing on having one's entire family and support groups ceasing to publicly acknowledge their existence.