He was a Labor Party member of the New South Wales Legislative Assembly from 1987 to 2003, representing the electorates of Heathcote (1987–88, 1999–2003), Burragorang (1988–1991) and Bulli (1991–99).
[citation needed] He left the Navy in 1971, and worked as a senior inspector with his local water board until his election to parliament.
[1] McManus entered state politics in 1987 after winning Labor endorsement for a difficult by-election, sparked by the resignation of former Labor minister Rex Jackson amidst a serious corruption scandal which would later lead to Jackson's imprisonment.
The race was made further difficult for Labor due to Jackson's surprise decision to run as an independent, but McManus survived a severe anti-Labor swing to take the seat ahead of Liberal candidate Allan Andrews.
[2] After a hostile electoral redistribution, McManus shifted to the safer seat of Burragorang at the 1988 general election,[3] where Andrews won Heathcote at his second attempt.