Several things are going on here. One, Cruz has defied and insulted Beltway insiders. Whatever his other failings, Trump hasn’t said unwelcome things at Senate GOP Conference lunches or voted the wrong way on a motion to recommit. So everything that makes Trump an unsuitable nominee can be overlooked, while Cruz is considered unacceptable.

Two, the insiders apparently don’t care much about principle or substance. The phrase they repeatedly use about Trump is that he will “get something done” — without specifying what the something is, or how he will do it.

Three, some Beltway Republicans have convinced themselves that Trump will be a better general-election candidate than Cruz. There is little evidence for this (Trump runs worse than other Republicans in general-election matchups), although one can always hope.

Four, there is a vein of cynicism running through the establishment. Some Republican professionals reportedly think Trump could effectively “rent” the party by winning the nomination and losing the general election. In this scenario, Trump would ease the way for a new Democratic president, yet do the GOP the favor of leaving its pooh-bahs to resume business as usual.

Finally, after months of Trump leading the polls, fatalism about him has set in.