After a bad-tempered campaign, two surveys on Wednesday gave the son of a bus driver a lead of up to 14 points over Zac Goldsmith, his multimillionaire rival from Prime Minister David Cameron's Conservative party.
Khan and Goldsmith, London mayoral candidates from different sides of the track
After a final rally with Cameron, Goldsmith campaigned overnight in a last-minute push for votes, meeting traders at the Billingsgate fish market and helping deliver milk at dawn in the upmarket district of Kensington.
Khan has distanced himself from a scandal over anti-Semitism in the national Labour party and has defended himself against attacks from Goldsmith for failing to condemn extremists.
There are ten other candidates to replace Conservative Boris Johnson as mayor, a position that has responsibility for transport, policing, housing and promoting economic development, but none of them have a chance.
An Opinium survey for the Evening Standard newspaper put Khan on 35 per cent compared to 26 per cent for Goldsmith. His lead lengthened once second preference votes were taken into account, to 57 per cent against Goldsmith's 43 per cent.
A second poll, by ComRes for LBC radio and ITV London news, put Khan on 45 per cent and Goldsmith on 36 per cent on first preference votes, moving to 56 per cent and 44 per cent on second preferences.
The race for the mayoralty has been marked by negative campaigning between two very different candidates.
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Khan, 45, is the son of a Pakistani immigrant bus driver who grew up in social housing and worked first as a human rights lawyer before rising to be a government minister.
Goldsmith, 41, an environmentalist and Conservative lawmaker, is the son of late tycoon financier James Goldsmith.
Khan has repeatedly been accused during the campaign of support for extremists, which his team has condemned as smear tactics.
There was fresh controversy Wednesday when footage emerged of a 2009 interview in which Khan said government attempts to engage the Muslim community could not just focus on "Uncle Toms".
A spokesperson said his use of the phrase, often used against black people to suggest they are subservient to white people, was a "bad choice" and he "regrets using it".
On a national level, Labour has been battling allegations that it has a problem with anti-Semitism, prompting leader Jeremy Corbyn to announce an independent review.
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