Response to Rob: Party Platforms and "Rules"

In response to Rob's post on whether a a Republican Party led by a pro-abortion politician would become a pro-abortion party: I thought it was fascinating that the editors framed their concerns in terms of setting "rules" and maintaining those boundaries: "Parents know that, when we make significant exceptions to significant rules, those exceptions themselves become iron-clad rules to our children. It’s the same in a political party."  I wonder if this might be something of a literary key to understanding the sources of ideological polarization?  It seems that if you think about the process of shaping and articulating a party platform as a process of articulating "rules" and maintaining those boundaries, that would have a significant impact not only on the choice of a party's rhetoric, but also it's capacity to imagine the more "problem-solving" dimensions of political life.  Thoughts?