"As to your question whether a segment of the GOP wants to intentionally lose a few major elections, with the hope that they'll wake up, realize the nuts they invited have spoiled (actually soiled) the party, and thus transform into an earlier, more moderate, far less nihilistic incarnation that would really govern...I don't think so."

I'm not so sure. I do believe there is an element in the Republican party that knows they have lost control of the situation to such an extent that a massive enema is required. I mean they went on television Thursday night and attempted to do this to Donny Trump:

Robert De Niro as Marco Rubio.

The entire enterprise was set up to try to off him and CNN appeared to be in on the hit. I mean I expected at any moment the crowd was going to pull out their AR-15s and fill the Donald full of several cases of cheap Wal-Mart bullets then wheel George up on the stage and let him run over the loudmouth that insulted both his son and his wife...Barbara probably would have been allowed to take the final head shot.

"But I don't think there is a concerted effort among sizable elements of any of these groups to willingly forgo the White House for even one term, not with Supreme Court justice appointments on the line."

I think there are many Republicans that are well aware this is a lost election for them. When they have to actively attempt to sink their front runner while knowing their other candidates can't win...well...I would say the realists in the party know something needs to change for them to be able to compete in any way. Check out Lindsey Graham here, he is joking around at the start but the sadness on his face at the end is the real thing...he knows this is no small problem.