Perhaps the closest historical analogy to the kind of post-presidency that lies ahead for Mr. Trump is that of President Richard Nixon, who left Washington in disgrace to avoid being impeached for his role in the Watergate break-in. (Mr. Trump, for his part, does not care for the comparison, exploding at aides who bring up the ex-president’s name, according to CNN.)

But Mr. Nixon, say those who’ve studied his post-presidential period, felt remorse for his actions, expressing regret that paved the way for the former president to rebuild his reputation as a best-selling author, foreign policy expert and elder statesman.

“Nixon actually felt a sense of responsibility for what had happened,” said Kasey Pipes, the author of a book about Mr. Nixon’s post-presidency. “He felt bad about it and publicly and privately would tell people: ‘I let you down. I let the country down.’”