LONDON — Last year, when the stalemate over Brexit was dominating the agenda, Prime Minister Boris Johnson of Britain appointed Dominic Raab, the foreign secretary, as his deputy and next-in-line.
Mr. Raab seemed to have all of the required traits: A true believer in Brexit, he had mostly steered clear of scandal and was never seen as a serious contender for the top job.
But now Mr. Johnson is in intensive care with the coronavirus. Brexit has vanished from the public’s radar. And Mr. Raab has been given the power to lead the British government through one of its greatest peacetime crises, putting him closer than anyone ever imagined to the role of prime minister.
That has startled some of Mr. Raab’s rivals at the top of government, who have raised doubts in British news reports about his fitness for the job. And with the virus tearing through Mr. Johnson’s administration, sending top lawmakers and advisers into isolation, it has thrust Mr. Raab into the role of settling cabinet disputes and reassuring an unnerved public as the government decides whether to extend a nationwide lockdown.
For Mr. Raab, 46, a wooden public speaker more at ease navigating the ideological disputes of Brexit than the delicate questions of health care capacity and stay-at-home orders, it may be an ill-timed ascent.
In a halting news conference on Monday, several hours before Mr. Johnson’s office announced that the prime minister had been transferred to intensive care, Mr. Raab struggled to explain why Mr. Johnson remained in charge from a hospital bed.
And he admitted having last spoken to Mr. Johnson on Saturday, suggesting either that the prime minister was sicker than the public had been told or that Mr. Raab was not close enough to Mr. Johnson to act as his stand-in during the crisis.
“Anyone who saw that press conference would have been reminded of his limitations as a communicator,” said Tim Bale, a professor of politics at Queen Mary, University of London. “Sometimes a crisis can see a caterpillar turn into a butterfly, but I rather doubt that will happen here.”
As the first secretary of state in Mr. Johnson’s government, Mr. Raab has formally been his deputy since Mr. Johnson won leadership of Britain’s Conservative Party last year. That left little doubt that he would be the government’s “designated survivor,” the stand-in should Mr. Johnson fall ill.
But his responsibilities have grown far more quickly than anyone expected. He has already led meetings with the powerful heads of each facet of the government’s coronavirus response this week. And he will lead cabinet meetings and make decisions on Mr. Johnson’s behalf if the prime minister cannot do so himself from intensive care.
Mr. Johnson’s office has said the prime minister is still breathing on his own and has not been put on a ventilator. But his prognosis remains uncertain, and the government has been cagey about his condition since he tested positive for the virus last month.
During his decade as a Conservative lawmaker, Mr. Raab’s most influential moment may have come in 2018 when he resigned from the cabinet of Mr. Johnson’s predecessor, Theresa May, after only four months in his job.
A hard-line Brexit backer, he resigned in protest of the draft withdrawal agreement that he had ostensibly helped to negotiate as Mrs. May’s Brexit secretary. In truth, he had only limited influence over the deal, which envisioned Britain keeping some distant ties to the European Union after Brexit. But he became part of a parade of pro-Brexit lawmakers angry at Mrs. May’s plan who helped force her to step down as Conservative Party leader and prime minister.
For Mr. Raab’s fans, his resignation was proof that he was a man of principle, a dyed-in-the-wool Brexit supporter who put his commitment to a Brexit deal cutting ties between Britain and the European Union above all else. To his detractors, it was evidence that he was a careerist, a weather vane politician who read the mood of pro-Brexit Conservative Party members and pointed the same way.
In any case, Mr. Raab soon joined the race to succeed Mrs. May, staking out a position as perhaps the most pro-Brexit candidate and expressing more openness than even Mr. Johnson to the idea of shutting down Parliament to enact a total split from the European Union.
But without Mr. Johnson’s celebrity or charisma, he finished in sixth place and endorsed the eventual prime minister.
That helped put him in the pole position to become Mr. Johnson’s first secretary of state, a mostly empty title in a government where other lawmakers, including the chancellor of the Exchequer, clearly have more power.
In a cabinet of intensely competitive rivals, many of whom had been vying for Mr. Johnson’s job, Mr. Raab’s middling result and his pro-Brexit bona fides made him an obvious choice for the job of most senior cabinet minister. With Brexit stalled last year, Mr. Johnson was eager to show the Conservative Party’s agitated base that, should anything happen to him, a fellow pro-Brexit traveler would be prepared to take over.
Mr. Raab has drawn criticism for his hard-line positions, especially comments he made in 2011 that feminists were “amongst the most obnoxious bigots” in Britain. He is seen as having stronger objections to government spending than Mr. Johnson, making him an odd person to be taking over at a time of enormous financial rescue packages.
But it helped his relationship with Mr. Johnson that some of his campaign staff members had worked on the Brexit campaign in 2016 with Mr. Johnson’s aides. And as a graduate of Oxford and Cambridge who went on to become a lawyer in the Foreign Office leading a team prosecuting war criminals, Mr. Raab was seen as a safe pair of hands.
“He’d put in a reasonable performance in the leadership contest but wasn’t really seen as a serious threat to Boris Johnson,” Professor Bale said. “If you’re going to appoint a deputy, or at least a de jure deputy, then someone who isn’t seen as a threat is quite useful.”