Australians support same-sex marriage by a margin of about two to one, today's Essential Report finds, but 40% of voters say it makes no difference to how they'd vote. Fifty-nine per cent of voters support allowing same-sex marriage, the same level as in February, compared to 55% in December and 60% in June 2014; 30% oppose it, compared to 28% in February and 32% in December. Greens voters support it 93%-3%; Labor 70%-21% and Coalition voters 49%-38%. Women are more strongly in favour of same-sex marriage, 64% to 25%, compared to men -- 54%-34%. However, it makes no difference to 40% of voters what the position of a candidate or party is on the issue.

Coalition voters are the ones most unlikely to change their vote for pro-same-sex marriage candidates, while 46% of Labor voters are a little or a lot more likely to vote for a candidate or party supporting same-sex marriage. Just 15% of all voters say they are much less likely to vote for a supporter of same-sex marriage, and 19% of Liberal voters. This appears to discredit the argument put forward by hardline same-sex marriage opponent Cory Bernardi, who has warned that there would be "huge consequences" for the Liberal party if it backed same-sex marriage in opposition to the party base. In fact, barely a fifth of Liberal voters are likely to change their vote, and those opposed to same-sex marriage are unlikely to switch to Labor, the only voting choice where their vote is unlikely to flow back to the Liberals.