The independent MP, who went into the campaign with a whisker thin margin of just 0.3 per cent due to a recent redistribution, told supporters that he was expecting to retain the seat of Sydney with a swing of eight or nine per cent.

Mr Greenwich secured 43.3 per cent of the primary vote as the night wore on, and was on track for a two party preferred figure of 60 per cent.

His closest rival, Liberal candidate Patrice Pandeleos, won about 32 per cent of the primary vote, ahead of Labor's 13.9 per cent and 8.3 per cent for the Greens.

"We know that Sydneysiders do not fit into a Liberal, Labor or Greens box and they fight for independent representation," Mr Greenwich said.

"Whatever the result is statewide, we know that the people of Sydney have not given Mike Baird any mandate to continue to tamper with inner city democracy."

Mr Greenwich first took office in a 2012 by way of a byelection after legislative changes forced long-sitting MP and Sydney lord mayor Clover Moore to choose between Macquarie Street and the town hall.

Cr Moore, a strong supporter of Mr Greenwich, was on hand to praise the "truly spectacular" win, which was 6.4 per cent up on her result in 2011.

Mr Greenwich dedicated the victory to his grandfather, Harrison, who passed away during the campaign.

"He is someone who has a great sense of justice, a great sense of leadership and someone who continues to inspire me," Mr Greenwich said.

But the emphatic win wasn't without its surprises.

A polling booth in Millers Point, site of the controversial government decision to sell off long-term public housing properties, was won by the Liberal Party.

"I think that shows the shifting dynamic in Millers Point now as a result of the government's sell off," Mr Greenwich said.