A new poll, which reflects how Londoners will actually vote, shows Khan stretched his lead over Goldsmith to 20 points.
Khan has increased his lead over Goldsmith, his closest rival, after distributing second preferences, according to the YouGov poll.
When London goes to the polls is two weeks time, voters will be given a first and second preference.
The election works under a supplementary vote system, meaning that if no candidate receives a majority of votes after all the first choices are counted, the top two candidates proceed, and the second votes of everyone whose first choice was eliminated are then counted.
So basically, the second choice is pretty important.
YouGov reckons that Labour is building on its core vote in London, increasing its nine point lead in the General Election last year to 16 points, pushed forward by national Conservative unpopularity.
Under a new weighting scheme taking into consideration likelihood to vote, and excluding don't knows, Khan has a 16 point lead over Zac Goldsmith. But as with the election itself, when neither candidate wins 50 per cent in the first round second preferences are reallocated – giving Khan a 20 point lead over Goldsmith.
The poll comes amid growing tension between the Goldsmith and Khan campaigns, with Khan backers alleging that Goldsmith's campaign has been divisive and preyed on islamaphobia.
Indeed, Goldsmith has been criticised for sending out leaflets to that effect, calling Khan "radical and divisive".
But as YouGov states, the strategy seems to have backfired, as Londoners are more likely to call Goldsmith divisive than Sadiq Khan.
And on key issues Khan is leading Goldsmith in perception. Both have pledged to improve the transport network, policing and tackle air quality. But in each of these areas Khan is thought of as more likely to deliver, according to the poll.