Peter Garrett, WTF are you thinking? I can just see the thought process here: "I'll change them from within". Poor, deluded fool!
The ALP is a single-minded organisation. They have one aim: to get into power. Anything else, morals, policies, personalities, will always be subordinate to the overwhelming will-to-power.
Surely Peter remembers 1984 when the ALP and Liberals did a preference swap to keep Garrett and his Nuclear Disarmament Party out of the Senate? (okay, okay, linking to a bunch of Trots probably isn't ideal, so for balance here's "How the Trots Destroyed the Nuclear Disarmament Party".
I confidently predict that Peter will leave Labor within a year, probably having helped Labor over the line. He may manage to shame them into implementing a few policies, but he won't be able to stand the rough and tumble of a powerful party in power, the inevitable compromises and paybacks of patronage to the rich and powerful.
Peter, I thought you were smarter than this. You could have done a lot better.