LONDON — Boris Johnson pulled out of the race to succeed Liz Truss as Britain’s prime minister on Sunday evening, ending a quixotic bid to reclaim a job he lost three months ago amid a cascade of scandals, and leaving his rival, Rishi Sunak, in a commanding position to be the country’s next leader.
The result of the contest will not be known until Monday afternoon at the earliest, and there is still room for further twists. Mr. Johnson did not endorse Mr. Sunak, and another ambitious candidate, Penny Mordaunt, remains in the hunt. But Mr. Johnson’s withdrawal removes much of the suspense from a race that was shaping up as an epic battle between the former prime minister and his onetime chancellor.
Mr. Johnson said he believed he had a path to victory, even though the BBC estimated he had lined up the public support of only 57 Conservative lawmakers. It was well short of the threshold of 100 required to be on the ballot, though he claimed he had 102 votes.
Whatever the case, he said in a statement, “I have sadly come to the conclusion that this would simply not be the right thing to do.”
Mr. Johnson, 58, said he did not believe that he could govern effectively without a unified Conservative Party in Parliament. Despite what he said were his efforts to reach out to Mr. Sunak and Ms. Mordaunt to create some kind of unity ticket, “we have sadly not been able to work out a way to do this.”
Mr. Johnson’s departure ends a feverish three days following Ms. Truss’s resignation in which he once again gripped public attention and dominated the political conversation. But his campaign never really gained momentum. Party leaders threw their support behind Mr. Sunak as a better option to try to unify a divided party and put the chaos of the last few months — much of it caused by Mr. Johnson — behind it.
For Mr. Sunak, the 42-year-old son of Indian immigrants, the dizzying events appeared to cap a remarkable turnaround in his fortunes. In September, he lost his leadership bid to Ms. Truss in a vote of the party’s members, despite winning the most votes from Conservative lawmakers. Now, he stands on the cusp of becoming the first prime minister of color in British history.
Mr. Sunak, who formally declared his candidacy on Sunday with a promise to “fix our economy,” had lined up at least 155 votes by late Sunday afternoon, according to a tally by the BBC, more than double the votes pledged to Mr. Johnson.
Beyond the numerical advantage, Mr. Sunak picked up multiple endorsements from people on the Conservative Party’s right flank. On Sunday morning, Steve Baker, a lawmaker who represents an influential group of euro-skeptics in Parliament, announced that he would support him.
“Boris Johnson would be a guaranteed disaster,” Mr. Baker told Sophy Ridge of Sky News. “We cannot allow it to happen.”
Later in the day, Suella Braverman, an immigration hard-liner who served briefly as home secretary under Ms. Truss, threw her support to Mr. Sunak, as did Kemi Badenoch, the international trade secretary and a rising star in the party.
For Mr. Johnson, who flew home Saturday from a vacation in the Dominican Republic to woo lawmakers, it was sobering evidence of how much has changed since he won a landslide general election victory in 2019. Despite winning endorsements from former members of his cabinet, he was not able to persuade the party’s right flank — traditionally the bedrock of his support — to back him.
Not only did many party leaders view Mr. Johnson as an intolerable risk, they also believed that Mr. Sunak, who ran the Treasury under Mr. Johnson, could bridge some of the bitter ideological rifts in the party, which were deepened by Ms. Truss’s turbulent six weeks in office. In the last contest, many on the party’s right flocked to Ms. Truss, which enabled her to beat Mr. Sunak.
Under the rules set out by the party, candidates are required to have nominations from at least 100 of the 357 Conservative lawmakers to advance to a second round of voting, which is among rank-and-file members of the party.
Candidates have until 2 p.m. Monday to gather nominations. On Monday, the party will hold two rounds of voting to winnow the field to one or two. If two remain, party members will cast online ballots later in the week.
Ms. Mordaunt, who is viewed as popular with the members, could still be a factor if she is able to cobble together the requisite 100 lawmakers. Having declared her candidacy on Friday, she insisted on Sunday that she was confident of lining up more than 100 lawmakers. But political analysts pointed out that even if all of Mr. Johnson’s publicly declared supporters switched their votes to Ms. Mordaunt, it would still leave her short of 100.
She said that she had rejected an appeal from Mr. Johnson to support him, while media reports said she had asked him to support her bid.
Mr. Johnson did receive endorsements from the current foreign secretary, James Cleverly, as well as a member of his last cabinet, Nadhim Zahawi, who served as chancellor of the Exchequer after Mr. Sunak resigned. (On Sunday evening, he switched his support to Mr. Sunak after Mr. Johnson’s withdrawal.)
Mr. Sunak’s departure in July helped set in motion the wholesale walkout of ministers that toppled Mr. Johnson after a series of scandals that included illicit parties at Downing Street during the coronavirus pandemic and Mr. Johnson’s defense of a Tory lawmaker accused of sexual misconduct.
“When I was Chancellor, I saw a preview of what Boris 2.0 would look like,” Mr. Zahawi wrote on Twitter. “He was contrite & honest about his mistakes. He’d learned from those mistakes how he could run No10 & the country better.”
Other observers were more jaded. They noted that Mr. Johnson and his allies claimed to have rounded up the votes of 100 or so lawmakers several times throughout the weekend without ever providing evidence that it was true.
British newspapers reported that Mr. Johnson tried to strike a deal with Mr. Sunak to join forces, meeting him on Saturday. But the shape of such a ticket was never clear, given Mr. Sunak’s lead among lawmakers, and the animosity between the two men made any cooperation look far-fetched.
In the statement announcing his candidacy, Mr. Sunak said his experience as chancellor would equip him to lead Britain through the economic challenges that loom. He promised a government of “integrity, professionalism, and accountability,” drawing a clear comparison with the ethical failings of Mr. Johnson’s tenure.
For all his success in winning over lawmakers, Mr. Sunak would still face a challenging job in resuscitating his party’s fortunes. The Conservatives are trailing the opposition Labour Party by more than 30 percentage points in polls. Despite his flaws, Mr. Johnson was still viewed by many as a proven vote-getter.
Mr. Sunak also must contend with a party still torn by factional feuds and divisions. The fact that Mr. Johnson was viewed as a potential leader, however briefly, attests to the residual hold that he had over the party, and the task that Mr. Sunak would face as a leader. Some political analysts were already asking if there would be a place in Mr. Sunak’s cabinet for Mr. Johnson.
On Sunday, it was Mr. Sunak’s turn to be the magnanimous victor. Mr. Johnson, he said in a statement, “led our country through some of the toughest challenges we have ever faced, and then took on Putin and his barbaric war in Ukraine.”
“Although he has decided not to run for P.M. again,” Mr. Sunak added, “I truly hope he continues to contribute to public life at home and abroad.”