The yes campaign has urged young voters to return their marriage survey forms. Photograph: Morgan Sette/AAP
A new poll finds that 77% of enrolled Australians have already returned their marriage law postal survey forms, a development that may take the heat out of the campaign.
The poll, conducted for the Equality Campaign by Newgate Research, found that, in addition to the overall turnout, about 69% of enrolled 18- to 24-year-olds had voted and posted their forms.
A further 17% of people in that age group said they had filled out their forms but were yet to post them, suggesting a total of 86% of young people will have voted if their forms are received before the 7 November deadline.
By comparison, just 34% of 18- to 24-year-olds took part in the 1998 postal ballot to select delegates for the constitutional convention on the republic.
A separate Reachtel poll released on Monday showed the yes side set for a thumping victory, with 64.3% of respondents saying they had sent back their ballot and voted yes compared with 15.5% who had voted no.
A further 6% have a ballot and planned to vote yes and 5.7% planned to vote no. Some 5.7% said they would not vote and 2.8% had not received a ballot.
A total of 16 million Australians are enrolled to vote in the marriage law postal survey, so the Newgate Research poll result implies about 12.3 million have already voted.
About 1.7 million Australians aged 18 to 24 are enrolled to vote. The poll suggests that 1.2 million have already voted and a total of 1.5 million will have voted if they return their ballots as they intend.
The poll, which surveyed 1,000 people from Monday to Thursday last week, also found that more than 80% of people aged over 65 had voted.
On Tuesday the Australian Bureau of Statistics will release an update on how many survey forms it has received. It is expected to show a majority of Australians have voted. The result will be lower than poll turnout figures because it takes two to six days for posted forms to be received.
The Equality Campaign’s executive director, Tiernan Brady, said the poll showed a “very high turnout” and Australia was on track to “smash” Ireland’s turnout of 64% in its referendum on same-sex marriage.
“People understand the power of their vote and [the poll] reflects what we’ve been hearing on the doors and phone calls … that the vast majority of people have voted,” he told Sky News. “The vast majority of people see that this is not a normal political question … They understand this is about real people’s lives, real people’s dignity.”
Brady urged young people and others who had voted and not returned their ballot “to make sure it goes in the post box or else it just won’t count”.
“We’ve always wanted a high turnout because we’ve always believed the Australian people are for marriage equality and to treat lesbian and gay people equally in law.”
The director of the Australian Christian Lobby, Lyle Shelton, told Sky News “it would surprise me” if the turnout was as high as 77% already, suggesting that “millions and millions of Australians are yet to cast their vote”.
Shelton welcomed a high turnout, labelling it a “a good thing for our democracy” and adding that anything over 60% would be “credible”.
“This is going to be a campaign about who can keep fighting right down to the wire on 7 November.”
Shelton said the no and yes campaigns were “on a unity ticket” that voters should have their say rather than leaving survey forms on the kitchen table or fridge.
Asked about the high turnout among older people, Brady said that “even though people over 65 might be less likely to support [marriage equality], there’s still a majority in support”.
“There isn’t one particular demographic where we don’t think we can win.”
On Monday Guardian Australia reported that the surge in enrolment, in which an extra 98,000 Australians put their names down to vote in the marriage law postal survey, was driven by young people, women and inner-city residents.