In an analysis in The Australian (“Plunging into brave new territory”, 5/12) on the political ramifications for the decision of the AOP National conference concerning same sex marriage, Rowan Callick, cites the views of demographer Bernard Salt, of KPMG who sees an analogy with the 1999 republican referendum.
He thinks that since then opinion has hardened against a ( politicians’) republic.
He said that the position of voters on same-sex marriage reflected not so much voting patterns or age or religious affiliation, as progressive thinking. 
…progressives v conservatives….
"It appeals very much to the progressive intellectual Left, which is aligned substantially with the Greens. The problem is that it rankles with the battler heartland, where it is a little too advanced of their thinking at the moment."But he said attitudes towards gay culture had changed dramatically in the past 25 years.
"In 1978, the Gay Mardi Gras in Sydney was very edgy. By 2000 it was broadcast on Sunday night prime-time TV. Middle Australia does get comfortable with such ideas, but does so in its own time. The intellectual Left and Right to an extent are supportive of this, but they are the early adopters and Middle Australia may not get there in 2011 or 2012."
The issue required "very fine political judgment, and I'm not quite sure we are there".Salt said that barely one million voters lived in Australia's inner cities — within 5km of the central business districts. The vast majority lived in the suburbs and were people with conservative values who struggled with such notions.
…republic…
He compared the situation with the republic issue in the late 1990s, which linked supporters in the intellectual Left and Right, Paul Keating and Malcolm Turnbull.
"But at the end of the day, 64 per cent voted against." (According to the Australian Electoral Commission 54.87% voted against the proposal.)
Salt is not convinced that Middle Australian thinking has yet moved on the republic yet, either. “In fact, it's probably hardened, given views on William and Kate, and admiration for the Queen.”
Sometimes an issue on which Australia appears close to agreement could take more than a decade to resolve, he said.
"Middle Australia struggles with what it views as a seismic shift. This is how it regards same-sex marriage."
..constitutional issue…
For the law to be changed to recognise same sex marriages, it is likely there would be a challenge to the High Court arguing that the Commonwealth had no power to do this.
It would be argued that the power with respect to marriage relates only to marriage as it has been traditionally understood, that is between a man and a woman.
If the High Court were to then find that the legislation was valid, there would be claims that the High Court was engaging in judicial activism.
It would be said that such activism would go against the original intention of the founders as approved by the people and that this was in effect a change in the constitution which should only be passed if it were agreed by the people in accordance with the constitution.