Former Prime Minister Bob Hawke has announced his stance as on same-sex-marriage, as an opinion poll shows support for the 'yes' side is dipping.
The former Labor prime minister and his wife Blanche d'Alpuget revealed they're voting 'yes' in a video for the Marriage equality campaign.
Hawke's message comes as a Newspoll shows support for the yes side has slipped to 57 percent.
The 'yes' campaign took part in a national door knock over the weekend, while debate erupted over a text message campaign urging a 'yes' vote.
"This is incredibly important for people, this is about their lives and their dignity and we have a duty as a campaign to do everything in our power to win this on their behalf," Equality Campaign executive director Tiernan Brady said on Sunday.
"We can't leave any stone unturned in our quest to deliver equality to people," Brady said when asked by Fairfax about the controversial text message campaign.
Anti-marriage equality campaigners have complained a text message campaign run on the weekend was an invasion of privacy.
"The campaign from the 'yes' side has become very invasive into people's privacy and into their lives," defacto leader of the no campaign, Lyle Shelton, told Sky News.
The Australian reported on Monday support for changing the Marriage Act fell from 63 to 57 percent, while the 'no' campaign increased its support from 30 to 34 percent over the past month.
But despite the 'no' side gaining some ground in the polls, punter support appears to very much still back a 'yes' result.
Online bookmaker sportsbet.com.au reports 55 percent of the money placed so far is in favour of a 'yes' result at $1.38.
'No' is paying $3.00, but has attracted more individual bets than the 'yes' side.
"The money is tipping a 'yes' result but there is a long way to go before the November result," said sportsbet.com.au's Will Byrne.
But Astro Labe, the 38-year-old anarchist who admitted headbutting Abbott, denied last week's attack had anything to do with SSM.
"That was just coincidental that someone had stuck a sticker on my jacket... It was not what I was thinking about," he told reporters last week.
"I saw (Abbott) walk back across the lawns and thought 'I'm never going to get the opportunity to headbutt that c**t again ... so I seized the moment."