LONDON — For more than two months, Prime Minister Boris Johnson has floundered in his response to the coronavirus — abandoning widespread testing, dragging his feet on imposing a lockdown, leaving nursing homes unprotected, and muddling his message about how to reopen the British economy.
But it took a rogue 260-mile car trip by Mr. Johnson’s closest adviser to turn the tide of public opinion against him.
The outcry over Mr. Johnson’s chief adviser, Dominic Cummings, showed no signs of abating on Tuesday, as a junior minister in Mr. Johnson’s government resigned in protest and several additional lawmakers from his Conservative Party called on the prime minister to dismiss Mr. Cummings, taking the total number of those who have gone public against him to more than 35.
Two new polls showed a sharp erosion of public support for Mr. Johnson and a wall of opposition for his aide.
The image of a powerful government official flouting the lockdown rules that Downing Street enforces on everyone else has struck a nerve in a way that Britain’s haphazard response to the virus has not. Unlike the mysteries of epidemiology or the technical details of testing, Mr. Cummings’s decision to decamp for his parents’ house in Durham, in the north of England, when others were confined in their homes, is easy to understand.
“I have constituents who didn’t get to say goodbye to loved ones; families who could not mourn together; people who didn’t visit sick relatives because they followed the guidance of the government,” observed Douglas Ross, the under secretary of state for Scotland, in his resignation statement.
“I cannot in good faith tell them they were all wrong and one senior adviser to the government was right,” he said.
Mr. Johnson showed no signs of abandoning Mr. Cummings, offering such an unequivocal defense, analysts said, that it likely forecloses the possibility of opening an inquiry into his conduct — one way the prime minister could have appeased critics.
He risked his political capital to send his aide out to the garden at 10 Downing Street on Monday to mount an unrepentant defense of his actions. Mr. Cummings said that with his wife showing symptoms of the virus and him fearing he would soon contract it, he wanted to line up care for his 4-year-old child with relatives in Durham.
On Tuesday, the British media remorselessly dissected Mr. Cummings’s account. They zeroed in on his claim that after he arrived in Durham and was bedridden for several days there, he drove to a scenic town more than 20 miles away to test his eyesight, which he said had been impaired by his illness, before embarking on the long journey back to London. The visit coincided with the birthday of Mr. Cummings’s wife.
Kay Burley, an anchor at Sky News, pressed an ally of Mr. Cummings’s, Michael Gove, on whether people with damaged eyesight should “get in a car and drive half an hour with your 4-year-old strapped in the back.” Mr. Gove, a senior Cabinet minister, allowed that Mr. Cummings could have skipped the excursion to the town, Barnard Castle, and driven straight to London.
That ordinary Britons were consumed by the picayune details of an unelected political strategist’s personal travels, on a day when new government statistics suggested that the death toll from the coronavirus was closing in on 50,000, showed why the Cummings affair poses such a threat to Mr. Johnson. It goes beyond the normal din of politics to become a topic for dinner table conversation.
In British parlance, it is a story with “cut through.”
“Sixty-five million of us have been locked up for weeks,” said Jonathan Powell, a former chief of staff to Prime Minister Tony Blair, “and this guy has the cheek to break the rules he created and then tell us he acted reasonably. That has a completely electric effect.”
Mr. Cummings’s effort to explain himself rallied his supporters, who include most prominent cabinet ministers, but failed to turn the tide either among other lawmakers or, apparently, the general public.
Mr. Johnson’s numbers have taken a hit as well. Another survey, by the polling firm Savanta ComRes, found that his approval rating plunged 20 percentage points in the last four days and now stands in negative territory for the first time since his landslide election victory in December.
For all of Mr. Johnson’s struggles in handling the coronavirus, the British public had been patient with him. His ratings surged after he imposed the lockdown on March 23 and peaked when he was admitted to an intensive care unit with the virus on April 8. After he was released from the hospital, and the spotlight shifted to Britain’s mounting death toll, his support began to weaken.
Unlike in the United States, however, where President Trump’s feuds with governors and his touting of dubious remedies have been polarizing, Britons have generally pulled together, showing their solidarity every Thursday night with a round of applause for the National Health Service. This week, critics are calling for people to boo Mr. Johnson before they cheer the health workers.
Criticism of Mr. Cummings has come from across the political spectrum and includes both the Conservative Party establishment and die-hard supporters of Brexit. “No Apology, No Regrets,” said the headline of the staunchly pro-Conservative Daily Mail, which ran 12 pages of coverage, most of it scathing.
Robert Hayward, a Conservative member of the House of Lords and a polling expert, said the episode angered traditional law-and-order Conservatives who do not take kindly to rule breaking. But it has had the same effect on some who voted for the Conservatives for the first time in December in northern, working-class constituencies — the so-called “red wall” seats historically held by the Labour Party.
“Boris Johnson successfully convinced a fair few people in the Midlands and the north that he was a different sort of Tory and my guess is that this group of people will be most offended by it,” Mr. Hayward said.
Some analysts suggested that the saga could do the same damage to the Conservatives as two other calamities in the party’s modern history.
One was the introduction of the poll tax in the 1980s, which crippled Prime Minister Margaret Thatcher and paved the way for her downfall in 1990. The other was when Britain crashed out of a European currency mechanism in 1992, which haunted Prime Minister John Major until he was swept out of power in 1997.
“This has that sort of potential, though whether it gets that far we can’t yet judge,” Mr. Hayward said. Certainly, he said, it was likely “to be damaging for months and possibly for longer.”