The Labour leader, who appears likely to suffer setbacks elsewhere in Britain, will be able to say that his party has recaptured one of the biggest prizes in British politics.
But if Khan wins he is planning to mark his victory, at least in the immediate aftermath, without Corbyn by his side.
Khan, who has been depicted by the Tories as the Corbyn candidate after nominating him in last year's Labour leadership contest, wants to show that any victory would have  been secured on his own terms.
Khan's decision to keep his distance from Corbyn, at least in the first few days after any victory, shows the widespread unease in the party about the Labour leader.
Some members of the shadow cabinet are comparing Khan's style of campaigning, which has involved reaching out beyond natural Labour areas to build up a wider coalition of voters, with what they regard as a hard-edged side to Corbyn's approach.
There was some unease among frontbenchers when Corbyn unveiled a poster for the English local elections with what they saw as the rather blunt message: "Elections are about taking sides. Labour is on yours."
Labour's posters and leaflets in London have used much gentler language.
But the Labour frontrunner in the mayoral contest is taking nothing for granted and is keen to avoid any sense of complacency in the final days of campaigning. He is warning his team that they must work hard to encourage Labour supporters to vote because a low turnout could help his Tory rival Zac Goldsmith.
The Labour frontrunner is loath to focus on the days after the election.
No plans have been finalised. But at the moment it looks like Corbyn may have to wait a few days to congratulate Khan in person if he succeeds in winning one of the largest personal political mandates in Europe, making him a pivotal figure in Labour's future.
If Sadiq Khan wins the London mayoral contest on Thursday he will probably throw a lifeline to Jeremy Corbyn.