In 2008, Mallard ran against sitting candidate Clover Moore for the popularly elected position of Lord Mayor, gaining 14% of the vote.

[8] Mallard has long been supportive of marriage equality, putting him in opposition to many party members, including the former Federal Leader of the Liberal Party and Prime Minister of Australia, Tony Abbott but putting him in support with the former Prime Minister Malcolm Turnbull.

Using parliamentary privilege, Lee Rhiannon, a Greens Member of NSW Legislative Council, accused Mallard of a second indiscretion by receiving illegal donations through provision of rent by a third party during the 2008 local government election campaign.

The Department of Local Government investigation cleared Mallard of allegations that he breached the council's code of conduct.

[12] In June 2021 Mallard was elected as Government Whip in the NSW Legislative Council and Parliamentary Secretary for Infrastructure and the Aerotropolis.

[16] Mallard was previously employed at Liverpool City Council as a senior advisor to the Mayor Ned Mannoun and former CEO John Ajaka.