So the political parties have become these weird, permanent, pseudo-governmental entities that no longer have consistent identities of their own, but are basically available for capture every 4 years.
That's how you get the "Republican Party platform" doing a full reversal on trade policy, international policy, health care, and a dozen other issues between 2012 and now.
The "Republican Party" today is just a shell--a collection of structural advantages that the Trump folks have won the the right to put on like a costume. Same with the Democratic party--Sanders just failed to win the costume.
What we need, is to regularly reset the requirements for political organizations, so that it's just as easy for new candidates to be supported by new organizations, as old parties.