Unlike Mr. Trump, whose personal attacks often go unanswered, the committee lashed back at Mr. Johnson. It accused him of “impugning the committee and, thereby, undermining the democratic process of the House” and “being complicit in the campaign of abuse and attempted intimidation of the committee.” It plans a special report into Mr. Johnson’s behavior during the inquiry.

While Mr. Johnson delivered a landslide majority for the Conservatives less than four years ago — and he remains popular in some Tory precincts — he has never had the kind of iron grip over the party that Mr. Trump has.

In September 2019, Conservative rebels staged an insurrection, blocking his plan to withdraw from the European Union without an agreement with Brussels. Last summer, Mr. Johnson was forced to resign as prime minister after the wholesale resignation of members of his government, amid the allegations about Downing Street parties and sex offenses of a senior Conservative official.

But not until this week has Mr. Johnson faced a reckoning for what his critics say is a career — first as a journalist and later as politician — built on bending the facts and gleefully disregarding the rules. For those who have known Mr. Johnson for a long time, the sense of satisfaction was palpable.

“It’s the first time where he has finally been caught out,” said Sonia Purnell, who worked with Mr. Johnson in the Brussels bureau of The Daily Telegraph in the 1990s and wrote a critical biography of him. “If he hadn’t been caught out today, that would have been pretty much a mortal blow to British democracy.”