While many of Britain’s predominantly right-wing newspapers remain hostile to Mr. Corbyn’s agenda, their tone has changed. Where the news media once pointed to his failure to sing the national anthem as evidence of his unsuitability for high office, recent articles have debated things like whether Mr. Corbyn is turning from vegetarianism to veganism (apparently he is not, though he is eating more vegan food).

The news media “were so amazed that the election did not turn out in the way they expected, and that Corbyn did better than predicted,” Professor Fielding said, “that they have been slightly falling over themselves” and into a “perspective which has gone slightly beyond reality.”

After all, Mr. Corbyn did not win the election, even when up against an opponent, Mrs. May, who proved to be one of the worst top-level campaigners in years.

To win a general election, he will have to reach out to new voters, and “whether he is in a position to go and win a majority in Parliament is an open question,” said Mark Wickham-Jones, professor of political science at the University of Bristol. “We know that the party can mobilize at election time, but whether that sense of Labour as a social movement can become a sense of Labour as a structured political party, we don’t know.”

At the conference in Brighton, which runs through Wednesday, so-called Corbynistas may vent their anger at centrist and right-wing lawmakers. But there is little sign of a concerted effort to deprive right-wing Labour lawmakers of their seats. That could mean that now that Mr. Corbyn’s leadership is secure, his priorities are shifting toward seeking control of the country, rather than the party.

That may be hard. By the time of the next election, the Conservatives are likely to have replaced Mrs. May with a more popular figure, and Mr. Corbyn and his agenda will probably face tougher news media scrutiny.

In policy terms, one crucial test is Britain’s withdrawal from the European Union, or Brexit, the dominant issue in British politics and one that divides Labour, albeit less than it does the Conservatives.