A new survey puts Governor Evans Kidero ahead of his six opponents eyeing the seat in the August 8 General Election.
According to the poll by Infotrak research firm, Dr Kidero enjoys a 35.3 per cent popularity rating.
The poll conducted between March 18 and19 indicates Senator Sonko would get 23 per cent of Nairobi votes if elections were held today.
Former Gatanga MP Peter Kenneth's popularity continues to grow, setting the stage for a bruising battle with his main rival in Jubilee nominations.
The poll puts the 2013 presidential candidate's popularity at 20.2 per cent, about three per cent shy of Senator Sonko's support base.
Former advisor to Opposition leader Raila Odinga, Miguna Miguna, is at number four with 1.2 per cent, while former Starehe MP Margret Wanjiru has a support of 0.9 per cent.
Businesswoman Esther Passaris enjoys 0.8 per cent support, while Dagoretti North MP Dennis Waweru is last at 0.6 per cent.
This is despite the fact that he was the first to launch his campaigns.
The popularity rating could, however, significantly change depending on how the aspirants package themselves ahead of the polls since 18 per cent of Nairobi voters are yet to decide whom to vote for.
Further changes in popularity are likely to be occasioned by Jubilee nominations and whether they will remain united after the primaries.
Sonko, Kenneth, Waweru and Margret have all submitted their nomination papers for Jubilee nominations.
Jubilee primaries are likely to be acrimonious after the leaders failed to settle on a candidate through consensus. The survey sampled 800 respondents in all the 17 constituencies.