A minister in the Cain government and President of the Victorian Legislative Council from 1985 to 1988, he resigned from the Labor Party in December 1987 and unsuccessfully recontested his seat in 1992 as part of the Geelong Community Alliance, a team of local independent candidates.
[2] In 1987, Mackenzie crossed the floor to vote with the conservative parties against Labor electoral reforms that he viewed as "blatantly political".
[6] Mackenzie sought to run for re-election at the 1992 state election under the banner of the Geelong Community Alliance, a group of independents he had founded and formally registered as a political party.
The alliance, which included radio announcer Roger Kent and former Geelong trades hall secretary Malcolm Brough, received significant local media attention, but was unsuccessful, as Mackenzie was soundly defeated by Liberal candidate Bill Hartigan and only Kent in the Legislative Assembly seat of Geelong polled well enough for his preferences to affect the outcome.
[10] A long-time campaigner for voluntary euthanasia, he has served as patron of Dying With Dignity Victoria and has been a frequent spokesperson in favour of law reform in this area.