LONDON — Breakfast starts at 8 a.m. and guests help themselves to croissants and juice before the sleek figure of Rishi Sunak, the British chancellor of the Exchequer, works his way around the crowded, oak-paneled dining room of his official London home, No. 11 Downing Street.
For Mr. Sunak, meetings with groups of Conservative Party lawmakers help him reach out and forge a network of support in Parliament. For the lawmakers, it’s a chance to meet someone many expect to one day move next door — to No. 10, the prime minister’s home.
Virtually unknown 10 months ago, Mr. Sunak’s vertiginous rise has surprised almost everyone in British politics — in all likelihood even the man who promoted him, Prime Minister Boris Johnson, whose approval ratings have plummeted during the pandemic.
“Rishi Sunak has the strengths that the prime minister so conspicuously lacks, not only basic competence, but a grasp of detail,” said Tim Bale, professor of politics at Queen Mary University of London, “and no one has mounted such an obvious, in your face, social media campaign as Rishi Sunak.”
It seems to be working. A recent poll of party members by the ConservativeHome website placed Mr. Sunak, 40, easily top of cabinet satisfaction ratings, while Mr. Johnson was almost bottom of the list.
Contrast that with a survey Professor Bale conducted last December in which Conservative Party members were asked who should take over were Mr. Johnson to step aside. “Just five out of 1,191 named Rishi Sunak,” he said, “and I’m not sure that all of them spelt his name correctly.”
When he was catapulted into his job in February, after two years as a minister — including six months in the No. 2 job at the Treasury — Mr. Sunak was firmly in the shadow of Mr. Johnson, who had just won a landslide election victory.
But while Mr. Johnson has floundered during the coronavirus pandemic, Mr. Sunak has been a beacon of calm and competence, intervening swiftly to spend billions of pounds supporting jobs as the economy went into lockdown free fall. With new restrictions coming into force in parts of the country, Mr. Sunak has announced new state support for affected areas and on Monday he gave a fluent defense of his latest measures at a media conference alongside Mr. Johnson.
Perhaps wisely, given the speculation about his ambitions, Mr. Sunak tried to burst his own bubble when the Conservative Party held its recent party conference virtually.
In a surprisingly short speech, he lavished praise on Mr. Johnson and warned that uncomfortable economic choices lay ahead. The subliminal message seemed to be: “You might like me a little less when all this cash has to be paid back.”
But right now, they like him a lot, and his appeal among nonpartisan Britons has been burnished through slick social media posts on Instagram and Twitter designed around “Brand Rishi.” Allies insist that Mr. Sunak is simply using digital media techniques to communicate more effectively rather than to promote his ambitions.
His posts stand out from the drab detritus of political advertising, though. Often they feature a stylish photograph of the chancellor endorsing a policy with his distinctive signature, rather like a sporting celebrity might promote an expensive fitness accessory.
This was probably not what Mr. Johnson expected when he promoted Mr. Sunak to take over from Sajid Javid, the previous chancellor who resigned after refusing to accept curbs on his right to hire his own advisers. Mr. Sunak agreed, leading some to speculate that he would be more compliant.
In Britain, the relationship between prime minister and chancellor — although a central pivot of government — is often one of rivalry and tension. So the idea in February was to ensure that there was one center of power on economic policy: in No. 10.
But few prime ministers can afford to fire two chancellors, so Mr. Johnson was taking a risk in appointing someone as adept and diligent as Mr. Sunak.
Not only is Mr. Sunak a smooth communicator but, with his Indian heritage, he is a walking success story of modern multiracial Britain.
His grandparents, originally from Punjab, arrived in England from British colonial East Africa in the 1960s. As a teenager, he says he suffered racist abuse. “It stung, I still remember, it’s seared in my memory,” he told the BBC, recounting how he had been abused in a restaurant.
But while Mr. Javid, his predecessor, was the son of a bus driver from Pakistan, Mr. Sunak’s father was a doctor and his mother ran a pharmacy. Together, they earned enough to send him to an elite private school, Winchester College.
Without that expensive education, Mr. Sunak might well still have reached Oxford University (he graduated with top grades). But his schooling seems to have helped instill the confidence and social polish that has allowed him to move effortlessly through the ranks of the Conservative Party.
Before his political career began in earnest, Mr. Sunak also earned an M.B.A. at Stanford University, where he met his future wife, Akshata Murthy, daughter of one of India’s richest men, the billionaire Narayana Murthy, co-founder of Infosys, an IT giant.
Mr. Sunak worked for Goldman Sachs and two hedge funds before being elected to Parliament in 2015. In the 2016 referendum on European Union membership, he voted to leave.
That decision sped his promotion through the ranks, though some hard-line Brexit supporters say that they suspect it was a tactical move and that they believe he is pressing Mr. Johnson to strike a trade deal with the European Union.
One of Mr. Sunak’s few political vulnerabilities is his wealth. There was barbed commentary when he was photographed with a $235 “smart mug” that keeps coffee or tea at a precise drinking temperature for up to three hours and when he described working out on an exercise bike that retails at around 10 times that amount.
But Mr. Sunak is generally good at avoiding gaffes and is well plugged into the media world. He was the best man at the wedding of a school friend, James Forsyth, and Allegra Stratton. Mr. Forsyth is the political editor of the Spectator, a conservative weekly, and Ms. Stratton is a former journalist and broadcaster. She is currently employed by Mr. Sunak as an adviser but is expected to become the spokeswoman for Mr. Johnson, in which capacity she will conduct televised news conferences.
Mr. Sunak’s allies see this as an illustration of the close ties between the Downing Street neighbors. But, while relations appear good at the moment, tensions have surfaced. Last month Mr. Sunak moved to protect the economy by fighting off many lockdown restrictions suggested by scientists advising the government.
Those differences are likely to grow.
Some day, Britain will have to start to repay its huge pile of debt. Mr. Johnson neither wants to return to austerity nor to raise taxes, but some decision cannot be delayed indefinitely.
Sophia Gaston, director of the British Foreign Policy Group and a fellow at the London School of Economics, said, “The chancellor has been in the privileged position of playing Father Christmas throughout the pandemic, one of the few politicians bearing gifts rather than taking them away.”
“Tax rises are on the horizon,” she added, “and he will soon have to take tough decisions about which industries to prop up and which parts of the electorate to shield from the worst of the pandemic’s economic hit.”
Should unemployment rise to levels not seen since the 1980s, Mr. Sunak would surely take at least some of the blame.
But, Ms. Gaston noted, he has already shown himself to be an outstanding communicator and a consultative and pragmatic leader. “If his branding can remain strong during the next six months of economic doom and gloom, there can be no limits on the scope of his political ambitions,” she said.
So far, Mr. Sunak has successfully distanced himself from the questions over competence that have gathered around Mr. Johnson and much of his cabinet.
He has also avoided the culture wars regularly stirred by some of Mr. Johnson’s pugilistic, pro-Brexit advisers, who seem never happier than when attacking the pillars of the establishment.
That leaves him neatly positioned as an exponent of a more competent and inclusive type of politics, an enticing package should a vacancy arise next door in Downing Street.
“In his position, you can’t afford to look too eager,” Professor Bale of Queen Mary University of London said. “But, on the other hand, you can’t afford to miss your moment when it comes.”