As many as four of Australia's most traditionally-minded electorates may be ignored by their MPs in a same-sex marriage vote in Parliament.
Nationals MP Mark Coulton revealed to the ABC that if the national vote climbs to 60 per cent in support of same-sex marriage, he is likely to ignore the result from his constituents in the seat Parkes in western New South Wales — even if they strongly back No in the postal survey.
"If the [national] vote comes in as being as predicted, or somewhere close to that 60 to 70 per cent [support], then I'd think that the majority of people will have spoken," he said.
However, Mr Coulton added that "if we get into the 50s [per cent support in the survey], then we're talking a different matter".
The postal survey will return both national and electorate-level results on November 15.
Of the 10 electorates least supportive of same-sex marriage according to the Vote Compass data, MPs in five have declared they would not support a same-sex marriage bill in Parliament.
One, Ken O'Dowd in the Queensland seat of Flynn, has indicated he will vote based on the result in his electorate.
Only Mr Coulton has declared his decision will be determined by a national result.
"Some of the people in my electorate will not like that decision, some of them will, but I actually think the point of having a plebiscite is for the Australian people to have a say," he said.
Three senior Labor MPs in Western Sydney — Chris Bowen, Jason Clare and Ed Husic — support same-sex marriage despite minority support for change in their electorates.
Mr Coulton described talking to his community about the issue as a "no-win situation", but Mr Clare, MP for Blaxland, said he was confident that his stance would not alienate voters.
Blaxland covers suburbs such as Auburn and Bankstown which having higher-than-average rates of religious faith.
"Back in the 2013 election campaign, an organisation put out flyers attacking me for voting for marriage equality in 2012, and it didn't change the vote, people still supported me," Mr Clare said.
"There will be some people that come up and say 'I don't support your position on this issue' and I will say 'fair enough, you're entitled to your opinion' —that's democracy."
Mr Clare's winning margin at the 2016 election was close to 20 per cent. His margin was 11 per cent in 2013.
Mr Coulton's Nationals colleague Andrew Broad said on Monday that same-sex marriage was a society-wide, not local, question and he would follow the lead of the Australian people as a whole.
"If the Australian society decides that they want changes to the Marriage Act, for me it's a societal question and we have to honour society," he said.
"People throughout their relationships move across electorate borders."