But this time, advisers noticed that the president, a man who has in the past relished the idea of leading his troops into political battle, seemed subdued. He appeared to realize the serious nature of what had just taken place, and yet his relative calm — contrasted with his more typical lashing out when he is anxious — unnerved some of his aides.

“We started with collusion,” the president mused, according to several people who witnessed Mr. Trump’s somber mood. “How did we end up here?”…

On Air Force One on Tuesday night on the way back from a rally in West Virginia, Mr. Trump repeatedly minimized the news, telling aides that the legal developments were not about him, but about Mr. Manafort and Mr. Cohen. He also groused over the optics of the rally, telling a person close to him that the crowd seemed flat and that some chairs were empty.

By Wednesday, Mr. Trump’s lawyers were arguing privately that Mr. Cohen’s admission and guilty plea to violating campaign finance laws was a punch but not a knockout blow, and were assessing what options they had for fighting back. They stressed that Mr. Cohen had said repeatedly in previous accounts that Mr. Trump was not aware of his payment to Ms. Clifford, known as Stormy Daniels.