In almost certainly the most expansive series of penalties he has incurred in his life, Mr. Trump’s Twitter account has been banned, his business brand badly dented, his presidency doomed to the historical infamy of a second impeachment. His largest lender, Deutsche Bank, is moving to create distance from him. His New Jersey golf club was stripped of a major tournament. Some once-reliable Republican congressional loyalists are revisiting their commitment, threatening his grip on the party, even as the president’s popularity with much of his support base remains undimmed.

Those who have known and watched Mr. Trump across the years cannot shake the irony of a president felled by the very formula that powered his rise: inflammatory speech and a self-regard that has congealed at times into functional self-delusion.

He has never considered words to be as significant as actions, or even in the same category of prospective offense. Words were whatever got him through the next interaction, people who worked with him say. Words were not deemed important enough to invite serious trouble.

So well-developed were Mr. Trump’s survival instincts, in theory, that he had all but perfected the art of semi-plausible deniability — an upside of being on seemingly every side of every major political issue at various points in his adult life.