Against a frustrated, profoundly un-WASP-like Republican electorate that craves the visceral pugnaciousness of Donald J. Trump or the outsider anger of Senator Ted Cruz, Mr. Bush’s family values — of cordial restraint, of civil discourse, of earnest public service — can seem almost quaint.

Mr. Bush tells voters who wonder why he cannot summon Mr. Trump’s TV-friendly fury that he “wasn’t brought up that way.” He struggles with a basic task in politics — bragging — conceding that, when he does, he feels “the looming presence of Barbara Bush,” his boast-averse mother. And in an age of topic-changing sound bites, he is oddly determined to respond to every inquiry…

C. Boyden Gray, who served as White House counsel under the elder Bush, ticked through the code of conduct the Bush dynasty has long embodied: “Civility and good manners were kind of assumed,” he said.

“You would be generous to a loser, you would not boast about your victory, you would be civil during an engagement, but you’d use every trick you had, every skill you had to win,” Mr. Gray continued. “They represented a whole generation of people, and I think a whole way of looking at things has been lost.”