Labour's Val Shawcross has been elected to the London Assembly as member for the Lambeth and Southwark constituency for a fourth consecutive term.
As Ken Livingstone's nominee for deputy mayor Ms Shawcross has stayed close to the Labour mayoral candidate's side throughout the campaign.
Mr Livingstone has promised to appoint her as chair of Transport for London if both are elected to City Hall.
A close finish in the Mayoral contest is now being predicted since the count began at 9am.
By 5.30pm on Friday counting indicated that Ken Livingstone had won 50% of votes in Lambeth and Southwark with Boris Johnson lagging behind with 30%.
The totals for the Assembly candidates in the Lambeth and Southwark seat are as follows:
Valerie Shawcross – Labour – 83,239 – 53% (2008: 60,801 – 36%)
Michael Mitchell – Conservative 30,537 – 19% (2008: 32,835 – 20%)
Jonathan Bartley – Green Party 18,144 – 12%
Rob Blackie – Liberal Democrat 18,359 – 12% (2008: 36,953 – 22%)
James Fluss – Fresh Choice for London 4,395 – 3%
Daniel Lambert – The Socialist Party (GB) 2,938 – 2%
Just 37% of those on the electoral registers of Lambeth and Southwark came out to vote on Thursday.