A few thoughts on the Republican Party.
I'm going to start by observing that I've taken, like, one class in political science and one class in game theory. Both were undergraduate classes. So take this post with a grain of salt.
Let's start with game theory. Imagine that three people are splitting up $10. A player proposes a division of the money, and it takes a majority (two votes) to win. It should immediately be obvious that the allocation of the money is going to depend on exactly how the proposals are made and the votes conducted. If only one proposal can ever be made, then it boils down to something similar to the "ultimatum game" in which one player can take almost all of the money. In other words, Player A would say, "I'll take $9, Player B gets $1, and Player C gets nothing." (Let's assume everything is done in dollar increments.) Player B will (probably) vote for this proposal, because otherwise he would get nothing. Player C can vote against it, but can't prevent it from being enacted.
However, imagine that any player can interrupt the proceedings at any moment with a new proposal. In that case, the outcome of the game is radically uncertain. Any two of the players can gang up on the third player and split the money between them, but which two will it be? A key insight here is that the excluded player can always make a better offer to one of the two colluders. So for instance, let's say Player A and Player B are splitting the money evenly, with Player C getting nothing. Player C could approach Player B and suggest a different split: $7 for Player B and $3 for Player C. Player B should take this offer, because he will get more than he would under his deal with Player A.
But Player A could then make Player C an offer: Player A gets $6 and Player C gets $4. This would make Player A and Player C better off at the expense of Player B.
You can play this game forever. This game has an "empty core," to use a term from game theory. We just don't know in the abstract how the money will be allocated. And in fact, if we set up a game like this, we might observe frenetic activity as the players try to cement together a stable alliance in the face of inherent instability built into the rules.
Now consider political parties and coalitions. If voters care about multiple issues, and are heterogeneous, then there are various ways you can draw the dividing lines between political parties or coalitions. The lines that divide these parties are called "cleavages." Right now, obviously, by far the biggest cleavage in U.S. politics is between the Democrats and the Republicans. But there are smaller cleavages that have emerged between various factions in both parties, and in some cases the cleavages extend across parties (for instance, each party includes a protectionist bloc).
Anyway where I am going with this is that cleavages aren't natural phenomena, they are caused by the choices that political actors make. Right now a variety of conservative players, dissatisfied with the status quo, are working to fracture the Republican coalition in a way that they believe will improve their standing once the dust settles. They believe that the new cleavages will elevate them personally or will promote their ideological vision. They don't necessarily agree with each other about anything in particular—what they have in common is the expectation that they will be better off in a different equilibrium. They are like Player B and Player C striking a deal to cut Player A out of the picture.
But the new cleavages may be very bad for the Republican Party as an institution. For a variety of reasons, the Democrats have built a coalition that for the moment is holding together fairly well. Meanwhile the Republicans are in open warfare with each other.
I'll write more about this, as I keep promising. For now I just want to observe that part of what is going on is the attempt to force a realignment within the GOP and across the parties to elevate the values and careers of the people doing the disrupting. And while the equilibrium has been stable for a long time, indicating that it probably isn't quite so radically unstable as my example above, I believe it is quite susceptible to the parasitic attack it is currently undergoing. The Republican Party has been sick for a long time, and now its immune system is rapidly collapsing.