Australia's upper house is more powerful than the House of Lords, which is what caused the issue to begin with. The Australian Senate can block supply, whereas the Lords can only delay it for a month.
Apologies for coming to this so very late. I think it important enough to comment on, however.
The government of Australia resides in the House of Representatives, i.e. The Commons. The Senate, purportedly, is the States' House of Review, though these days, political parties dominate not the individual States' interests.
If the Senate declines to pass any Bill, twice, then the PM, the Leader of the House of Representatives, may call a a double dissolution. Parties which may be in the minority in the House of Reps but may control the Senate generally don't like this as a double dissolution, ie. a full Senate and House of Representatives election, invariably ends with one party, usually Labor, dominant in the Senate. The party presenting the obstacle usually fares poorly.
In my opinion, Australia is a naturally and traditionally conservative Labor nation due to historical formations. Because of our unique voting system (compulsory universal voting, and a preferential system) Labor doesn't always win, even if that party generally obtains the most primary votes. What it does mean in practical terms is that the conservative coalition partners often end up with preferential votes which tip them over the line (neither coalition party would ever have a hope of succeeding under their own steam).
1975 was an aberration. The Governor-General spoke to HM first. When the PM subsequently rang her, she said that now there was nothing to be done as
her representative had already acted. This will never, ever, happen again. HM was, reportedly, singularly distressed over this controversy, and, allegedly, upset that this had occurred in 'her name'.
In legal circles this has always been a contentious issue and not only because immediately the GG installed the opposition leader as PM, a vote of 'no confidence' was carried in the House of Reps denying him the position, but with the GG' support, the erstwhile Opposition Leader was empowered to continue as PM. In our inherited Westminster system, this was the first and only time where this had occurred, anywhere in the world, and was in total negation of Runnymede, which has formed the basis for governance throughout Britain and her empire for 800 years. At a personal level, and even though I would certainly not have supported the government which was dismissed, as I am a believer in the rule of law above all, I remain disgusted and outraged at what eventuated. To me, it's a blot on Australia's constitutional history and I despise those who traduced our valuable and incomparable Westminster traditions for what proved to be short term gain.
In a legal sense, it has been an open sore for some time. Some blame HM, entirely, others blame the Constitution, and a few blame those who, allegedly, pocketed huge sums of money over the 'deal'.
The new Australian Labor PM has said that he won't press for a republic in this term. He doesn't seem to think that it's vitally important compared to his 'democratic Christian' agenda. What I think will probably happen is that within a few years, we'll be asked,simply, if we wish Australia to be a republic, details to be worked out later. If and when that occurs, the answer will be, in my opinion, a resounding 'yes'. Last time, the vote had entirely demarcated into a futile debate over the mechanism for electing a President, which is why it was lost.
To end where I began.....the Senate does
not hold stronger powers than the House of Reps. Our government is formed by whoever holds the majority in the House of Representatives.
The Whitlam government, which would have lost the next election anyway, was dismissed only and entirely by the Governor General, and to my mind, this wasn't acceptable. It did, though, unfairly, hammer the last nail into Australia's royal coffin. It's very sad but a truism, that The Crown, in a constitutional sense, is held, by many, eminently culpable in all of this. Poor Queen Elizabeth was caught, right royally, between a rock and a hard place!
To those who repeat, 'if it ain't broke, don't fix it', I can only reply that many of my friends and family, generally speaking, a politically conservative crew, almost to a man and woman want Australia to be a Republic. 1975 looms large in their perspective, and all that's saved The Crown, I believe, is the admiration which is genuinely felt for our Queen.
And although I like her and think her a great asset to the Royal Family, the bottom line is that most Australians, or at least those with whom I discuss these matters, just don't like Camilla and simply will never accept her as Queen. On the other hand, neither she nor Charles needs Australia, so who's the most to lose?