I've come to this thread late so forgive me if I go over ground covered. The major population similar but not the same as Australia who decided on this issue were the Irish. It passed on a plebiscite with the usual virulent pro and anti, religious and rainbow; opponents forming about 40%, probably 50% as the rainbow were better organised and religion is not all that popular in the Land of Saints and Scholars atm. This left 50-60% of voters. The main reason it passed was that many of the 50-60% had family members who were gay, uncles, aunts, nieces, nephews, sons and daughters, fathers, mothers, grandparents, friends who were gay. Ireland though diluted by the EU is still a reasonably homogenous society and much of the discourse was conducted outside of the media, amongst friends and family. We in Australia unfortunately have a very fractured political entity, poor family strength and a media which thrives on the rare, the freaks and the identity or socially committed outwith of family ties. I do not know how a plebiscite would go here. A NO vote would be more problematic as the rainbows are more committed socially and economically and would plague the issue. A YES would be the best, but Australia being so polarised atm, the delay in having the plebiscite, fed by the rainbow, would mitigate against this outcome. That is my take on it anyway.