Another brother, Neil Mackerras, was active in the Democratic Labor Party in its early years.
In 1974 Mackerras was employed in the Department of Government at Royal Military College, Duntroon by the University of New South Wales.
During his stay in the US in November–December 2000, there was a "snap" election in Canada, which he visited, enabling him to improve his knowledge of Canadian politics.
Indeed, one of the reasons for his determination on the November–December 2000 North American visit was to study all the legal manoeuvres in connection with the only "cliffhanger" presidential election of the 20th century.
He visited the US again in September 2004 to attend the Annual Meeting of the American Political Science Association in Chicago.
His two most recent books are Australian Political Facts: Second Edition (Macmillan, 1997) which he wrote with Ian McAllister and Carolyn Brown Boldiston and, more recently, Constitutional Politics: The Republic Referendum and the Future (University of Queensland Press, 2002), which he edited with John Warhurst of the Australian National University.
The two men took opposite sides in the debate over the 1999 Australian republic referendum but have now joined to record the event.
An example of an incorrect prediction was the one he made in The Australian on 1 November 2004: he said that John Kerry would defeat George W. Bush in a landslide in the U.S. presidential election the following day, and specifically predicted that Kerry would carry Florida, Ohio, Nevada and Missouri.