This rightward lurch—behind an almost certainly hopeless cause of constitutional change—captures the core GOP dilemma now unfolding in the party's nomination contest.

The Republican electoral coalition now relies on preponderant majorities from the groups most unsettled by demographic and cultural change: older, noncollege, and rural whites. There are no longer enough of those voters to guarantee Republicans a national majority; that's why Democrats have won the popular vote in five of the past six presidential elections. Yet, as Trump's rise shows, many of those voters militantly oppose the policies (like immigration reform) that might help the party expand its coalition.

Trump's rise behind his belligerent immigration agenda has horrified many conservative thinkers. Perceptive conservative essayist Ben Domenech recently warned that Trump is leading the GOP "toward a coalition that is reduced to the narrow interests of identity politics for white people."