Keir Starmer Is on the Cusp of Power in the U.K.

Keir Starmer, the leader of Britain’s Labour Party, nodded sympathetically as a young mother recalled, in harrowing terms, how she had watched closed-circuit television footage of the fatal stabbing of her 21-year-old son, whose heart was pierced with a single blow.

“Thank you for that,” a somber Mr. Starmer said to the woman and other relatives of victims of knife attacks, as they stood around a wooden table last week, discussing ways to combat violent crime. “It’s really, really powerful.”

It was not the most feel-good campaign event for a candidate the week before an election that his opposition party is widely expected to win. But it was entirely in character for Mr. Starmer, a 61-year-old former human rights lawyer who still behaves less like a politician than a prosecutor bringing a case.

Earnest, intense, practical and not brimming with charisma, Mr. Starmer finds himself on the cusp of a potential landslide victory without the star power that marked previous British leaders on the doorstep of power, whether Margaret Thatcher, the 1980s free-market champion, or Tony Blair, the avatar of “Cool Britannia.”

And yet Mr. Starmer has managed an arguably comparable political feat: Less than a decade after entering Parliament, and fewer than five years after his party suffered its worst election defeat since the 1930s, he has remade Labour with ruthless efficiency into an electable party, pulling it to the center on key policies while capitalizing on the failings of three Conservative prime ministers.

“Don’t forget what they have done,” Mr. Starmer told a rally in London on Saturday, pacing the stage in a pressed white shirt with sleeves rolled up. “Don’t forget party-gate, don’t forget the Covid contract, don’t forget the lies, don’t forget the kickbacks.”

In listing this parade of Conservative scandals and crises, he brought the crowd of 350 to its feet. But it was a rare moment of fire, which captures the conundrum of Mr. Starmer.

The polls that predict his party will win a lopsided majority in Parliament onThursday also suggest that he is unloved by British voters. They struggle to warm to a man who seems less at ease in the political arena than in the courtroom where he excelled.

“He doesn’t do the performative side of politics,” said Tom Baldwin, a former Labour Party adviser who has published a biography of Mr. Starmer. While other politicians aspire to soaring rhetoric, Mr. Starmer talks earnestly about practical problem-solving and placing building blocks on each another.

“No one’s going to watch that,” Mr. Baldwin said. “It’s boring. But at the end of it, you might find he’s built a house.”

Jill Rutter, a former senior civil servant who is a research fellow at the London research group U.K. in a Changing Europe, said: “He has been ferociously — some would say tediously boring — in his discipline. He’s not going to set hearts racing, but he does look relatively prime-ministerial.”

Raised in a working-class family in Surrey, outside London, Mr. Starmer did not have an easy childhood. His relationship with his father, a toolmaker, was distant. His mother, a nurse, suffered a debilitating illness that took her in and out of the hospital. Mr. Starmer became the first college graduate in his family, studying first at Leeds University, and then law at Oxford.

His was a left-wing household. Mr. Starmer was named after Keir Hardie, the Scottish trade unionist and Labour’s first leader. He later recalled wishing as a teenager that he had been called Dave or Pete instead.

As a young lawyer, Mr. Starmer represented protesters accused of libel by the fast-food chain McDonald’s, rose to become Britain’s chief prosecutor and was awarded a knighthood. Even then, he used his legal brain to convince judges rather than courtroom theatrics to sway juries, a plain-vanilla reputation that followed him into politics.

Boris Johnson, the former prime minister, who debated him in Parliament, once labeled him “Captain Crasheroonie Snoozefest.”

Mr. Starmer may lack his rival’s glib one-liners, but he turned his forensic skills on the scandal-scarred Mr. Johnson, helping to expose untruths he told about Downing Street parties held during Covid lockdowns.

When Conservatives questioned whether Mr. Starmer, too, had violated lockdown rules by having a beer and an Indian takeout dinner with colleagues in April 2021, he vowed to step down if the police found he had been in the wrong. He was cleared — an episode that allies said showcased his rigorous adherence to the rules and offered a stark contrast to the leaders of the Conservative Party.

But Mr. Starmer’s political compromises have raised questions about his approach. He served the left-wing former Labour leader Jeremy Corbyn, taking charge of Brexit policy at a time when many of the party’s moderates refused to join his team.

When Mr. Corbyn stepped down after losing in 2019, Mr. Starmer positioned himself as his successor, winning on a platform that included enough of Mr. Corbyn’s policies to placate the party’s then-powerful left-wing.

Once elected, however, Mr. Starmer seized control of the party machinery and executed a remarkable pivot to the political center. He dropped Mr. Corbyn’s proposal to nationalize Britain’s energy industry, promised not to raise taxes on working families and committed to supporting Britain’s military, hoping to banish an anti-patriotic label that clung to Labour during the Corbyn era.

Mr. Starmer also rooted out the antisemitism that had contaminated the party’s ranks under Mr. Corbyn. Though he has not drawn a link between that and his personal life, his wife, Victoria Starmer, comes from a Jewish family in London.

Ms. Starmer, who works as an occupational health specialist for the National Health Service, is an occasional presence on the campaign trail. The couple have two teenage children, whose privacy they guard fiercely. In keeping with his wife’s heritage, the family sometimes observes Jewish traditions at home.

In exiling Mr. Corbyn, Mr. Starmer displayed a ruthless side. He even blocked Mr. Corbyn from running for his seat as a Labour candidate, although he is campaigning as an independent. Mr. Starmer’s aides have tightly controlled the list of those allowed to run for Parliament, weeding out other candidates seen as too left wing.

Allies of Mr. Starmer say he is aware of his limits and works hard to address his weaknesses. While he is not a natural orator, his speeches have improved since his early days in Parliament, when one critic likened his performance to “watching the audience at a literary festival listen to a reading of T.S. Eliot.”

And, yet, the reputation for dullness lingers.

“How does Keir Starmer energize a room?” Gillian Keegan, the education secretary, asked recently before delivering her punchline: “He leaves it.”

The criticism rankles. “He doesn’t like the boring tag,” Mr. Baldwin said. “No one likes being called boring; he really doesn’t like it.”

Mr. Starmer’s friends describe a man with a sense of humor, a heathy home life and genuine passions outside politics. Despite knee surgery, he still plays soccer regularly and competitively (often reserving the playing field and selecting the team). He is an ardent fan of Arsenal, the soccer club that plays not far from his North London home.

In some ways, Mr. Starmer has been helped by his relatively recent arrival in Parliament. He was not caught up in the internecine feuds of previous Labour governments or tainted by allegiances to former leaders like Gordon Brown and Mr. Blair, though he and Mr. Starmer now have a blossoming relationship.

There are disadvantages, too. There are relatively few Starmer loyalists who are willing to fight in a foxhole with him. The same lack of passion extends to many voters. They may find Labour less objectionable than it was under Mr. Corbyn, but that does not mean they are casting their votes with excitement.

“Keir Starmer’s objective was to stop giving people reasons to vote against Labour, and he has been very successful at it,” said Steven Fielding, an emeritus professor of political history at the University of Nottingham in England. “He has been less good at giving people reasons to vote for Labour.”

The same sense of incompleteness hangs over even those who admire Mr. Starmer. Despite the many hours Mr. Baldwin spent with him researching his biography, he said there was “something slightly unreachable” about the Labour leader. “He’s a very tightly bound person who doesn’t trust easily,” Mr. Baldwin said. “He’s not emotionally diarrhetic.”

While Mr. Starmer has begun talking more about his personal story, his frequent references to being “the son of a toolmaker” growing up in a “pebble-dash semi” — his modest semidetached family home — can come off as perfunctory, even robotic.

“He doesn’t see why he needs to put him and all his inner workings on public display,” said Mr. Baldwin, who said he sometimes struggled to get more than monosyllabic answers from Mr. Starmer on personal questions. Once, he recalled asking him to elaborate on his feelings about an incident that had anguished him.

The response was concise, direct and of little help. “‘I was,’ Mr. Starmer said, according to his biographer, “‘very upset.’”