For Mr. Trump, the day after found him still a little shellshocked, according to people close to him. Despite the clear momentum behind impeachment among Democrats in recent weeks, some of Mr. Trump’s advisers tried to convince him — and themselves — that Speaker Nancy Pelosi did not have the votes and might not even bring the articles of impeachment to the floor, despite warnings from the White House director of legislative affairs, Eric Ueland, that the votes were there.

Mr. Trump’s aides packed his schedule with events to keep him out of Washington as the debate took place on Wednesday. He vented his fury at a rally in Michigan that started even as the votes were being recorded. But having gotten his emotions off his chest, he was unusually talkative flying home on Air Force One. Impeachment “doesn’t feel like anything,” he told aides, according to one person briefed on the conversation.

However much the humiliation and the ensuing news coverage stung, Mr. Trump was intent on not showing it — even in private.

By Thursday morning, he was eager for information. He watched television coverage, listening for clues about what Ms. Pelosi might be up to. Almost as soon as she said she might delay sending the articles of impeachment to the Senate, Mr. Trump started surveying advisers about what it could mean. “Why do you think she’s doing that?” he asked one person after another.