I have only one clarification, but it's an important one. Cost:
The “New Politics” reformers of the early 1970s thought they were sending the power to nominate back to the people, but that didn’t really happen. The people have some power, no doubt, as exercised through the primaries and caucuses, yet the party establishment still retains significant control. Through the money and endorsements that are dispensed over the course of the invisible primary, they determine who is and who is not a viable candidate – and it is from this list that the voters ultimately must make their choices.Exactly, but for one word: establishment. Party actors choose, and voters at best choose from the remaining choices. But whether those party actors are "establishment" or "insurgents" or "base" or whatever is entirely up in the air. As regular readers might notice, I've adopted the term "party actors" to account for all of them. I can note, for what it's worth, is that in my experience the overwhelming majority of those party actors on both sides of the partisan aisle do not think of themselves as the establishment -- that's always those other folks. At any rate, references to "establishment" actors undervalues, in my view, how permeable the ranks of relevant party actors really are, and how easy it is for influence to shift among them over time. The important distinction isn't between establishment and non-establishment; it's between party actors and voters-as-voters.
What's happening now is two things, simultaneously. Republican party actors are coordinating on their choices for nominee. But those individuals and groups are also competing for influence within the party (and therefore over who gets the most say in choosing the nominee). To the extent that the party is mostly stable, then it's just a coordination problem, but parties are not usually all that stable -- or, at least, there are usually multiple party actors who don't want to respect their place in the old status quo. All of which is why presidential nominations matter so much, and why they are great stories.