Ryan Lizza has a thoughtful piece in the New Yorker entitled Life of the Party: Can the G.O.P. save itself? It is an interesting exploration of how the nominating process has evolved over recent decades, and the problems that evolution has created.
As near as I can tell, the Republican Party is hell-bent on become a fringe party. Its current base is certainly energetic, but hardly large enough to give it a majority in a Presidential election, or even give it control of Congress. Yet the party seems more and more determined to exclude anyone who doesn't agree absolutely with all of its social and political views. That seems to me a recipe for disaster.
Here we have a party who simultaneously argues that government interferes too much in our lives, and yet wants government to enforce on everyone all sorts of (their own) social and religious positions. Here we have a party periodically horrified about the possibility that someone might impose Sharia law on all Americans, yet perfectly willing to impose Christian principles on all Americans. Here we have a party outraged by the growing Federal debt, yet unwilling to do anything effective (raise taxes, cut subsidies, reduce entitlements) about the problem.
Of course, if the state of the Republican party weren't worrying enough, the Democratic Party is just as nutty and out-of-touch on other issues, but at least it doesn't seem to be (currently) self-destructing.