Queensland Opposition Leader Tim Nicholls has voted in favour of same-sex marriage but said it was a difficult decision.
The LNP leader told reporters in Brisbane on Sunday he had filled out his postal survey earlier that morning, after a lot of "interesting" discussions with his wife and three teenage children.
"This has been really hard for me," he said.
"I come from a traditional marriage, a traditional background."
Mr Nicholls said ultimately it was St Paul's letter to The Corinthians, in the bible, which swayed him in favour of marriage equality.
"He says faith, hope, love and the greatest of these is love," he said.
"And on that basis I voted yes."
Meanwhile the Equality Campaign's Queensland director Peter Black said the organisation "made no apologies" for a text message sent to thousands of Australians over the weekend, encouraging them to support the yes vote.
"We are doing everything we can in our power to reach the Australian public," he said in Brisbane on Sunday.
Mr Black said it was one of the standard tools available to a political campaign.
"The numbers were computer generated, there's been no privacy invasion at all," he said.
Almost all postal surveys have been sent to every person on the federal electoral roll, with the Bureau of Statistics to release the result on November 15.
