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Jeremy Corbyn, the newly elected Labour Party leader, was greeted by supporters in Parliament Square in London on Saturday.Credit Andy Rain/European Pressphoto Agency

Jeremy Corbyn, the new leader of the opposition Labour Party, has stopped wearing T-shirts in public and now favors blue shirts and darker jackets. But even with his more prime ministerial attire, it is difficult to imagine a British electorate that just handed Conservatives a parliamentary majority turning to a party that has lurched so far to the left.

Instead, Mr. Corbyn’s resounding victory in his party’s leadership election makes it highly likely that Britain’s next prime minister will be the Conservative politician George Osborne, 44, the chancellor of the Exchequer and second in command to Prime Minister David Cameron.

Mr. Cameron, having just won another five-year term, has confirmed that he will not run for a third term and intends to step down before this one ends. In the unsentimental Conservative Party, that means the maneuvering to succeed him has already begun, with a change expected sometime after Britain votes in a referendum on whether to remain in the European Union.

That vote must happen before the end of 2017, but may take place sooner. With the British economy going well, and assuming that the Conservatives do not self-destruct over internal disputes on European Union membership, Mr. Osborne is considered the person most likely to lead the party into the 2020 elections.

His main rival, Mayor Boris Johnson of London, is engaging and popular with the public, but less so with his fellow members of Parliament. And with the Labour Party now leaving the center of politics wide open, it may be much easier for Mr. Cameron and Mr. Osborne to move Tories closer to that aspirational center, arguing that they have created jobs and pared down the budget deficit, and are a safer set of hands than an “old-style” Labour socialist.

Mr. Corbyn, 66, is consistent and sincere, a professed man of the “hard left” who believes that the Labour Party must return to its roots in the working class and fight inequality in all its forms. He is a sharp critic of American foreign policy and of Israel; he wants Britain to abandon its nuclear deterrent and has favored quitting NATO.

His resounding victory has energized a party in the doldrums after the fiasco of May’s elections, when Labour was nearly shut out of Scotland and had one of its worst showings in decades. He appeals to the angry, insurgent mood among trade unionists and many young people over inequality in capitalism, a sentiment that helped parties like Syriza in Greece and Podemos in Spain. In a sense, he is a left-wing response to the kind of alienation that helped the United Kingdom Independence Party, or UKIP, win nearly 13 percent of the vote in May, though it only won one seat in Parliament.

But as UKIP shows, strong minority parties do not produce many legislators in Britain’s electoral system, and the Labour Party was already, under Ed Miliband, considered too left-wing and too unreliable to get the seats in southern England that it needed for victory, even if propped up by the Scottish National Party. Those concerns will be only more entrenched now.

Mr. Corbyn is also going to have a very difficult time keeping Labour together. Already, the two leadership candidates of the center, Yvette Cooper and Liz Kendall, have said they will not serve in his shadow cabinet because of strong policy differences. Mr. Corbyn, who has made his career since he was elected in 1983 by voting against his party’s orders, is also opposed by most of Labour’s 232 members of Parliament. Even to get the 35 nominations he needed to run in this leadership election was a struggle, and some of those who nominated him did so simply to broaden the debate, with no idea that Mr. Corbyn would end up their leader.

Mr. Corbyn needs to appoint a shadow cabinet — members of Parliament who would be ministers if the party were in power and speak for the party on all issues — of 26 legislators, with another 60 or more shadow junior ministers. It is not clear how easy that is going to be.

For the moment, talk of any breakaway party is muted — after all, when the Social Democrats broke away from Labour in 1981, they were well-known moderates with government experience who were considered the new center of British politics. In the end, the Social Democrats effectively dissolved just seven years later, joining with the Liberals to become the Liberal Democrats. And the Liberal Democrats were just trounced in May for the sin of sharing power in a coalition government with the Conservatives.

Many Labour legislators will want to remain, not just to keep their seats, but to fight for Labour’s future as a mainstream party. Mr. Corbyn is 20 years older than his leadership competitors, and many will prefer to see his leadership as a temporary blast from the past — to the policies and rhetoric of the disastrous 1983 campaign of Michael Foot.

Still, once elected, Mr. Corbyn may be hard to dislodge before the next general elections. And he may be very useful in poking holes in Conservative positions and at skewering Mr. Cameron during weekly prime minister’s questions in Parliament, on issues ranging from refugees and foreign policy to social inequality.

The Conservatives are hardly immune. Their party is deeply divided over Britain’s membership in the European Union, and Mr. Cameron has a majority of only 12 seats, which he must manage carefully. If the Conservative Party does split over Europe, it is not inconceivable to imagine a new party of the center.

And today, that is no more inconceivable than the prospect of Mr. Corbyn becoming Labour leader was even three months ago.