Clover Moore has cruised to victory and a record fourth term as Sydney's lord mayor in a landslide, picking up a swing of nearly 10 per cent in her primary vote, as the Liberal party lost a key source of support in Sydney's west in an election night Labor said had "blown up" in Premier Mike Baird's face.

Cr Moore declared victory shortly after 9pm before jubilant supporters on Castlereagh Street. "This is a real win for grass roots democracy," she said.

With more than a quarter of votes in the Mayoral contest counted, Cr Moore was streaking ahead with nearly four times the vote of her nearest rival, Tony Abbott's sister Christine Forster.

Despite fears the addition of more than 20,000 businesses to council rolls could weaken her chances, Cr Moore was on track for a primary swing toward her of nearly 10 per cent in her fourth term.