Australian Prime Minister Kevin Rudd has delivered a strong defence of gay marriage on live television, days before the 7 September election.
In a Q&A session on ABC News, Mr Rudd said he backed gay marriage after "years of reflection in good Christian conscience".
His defence ignited debate and was praised by gay advocacy groups.
Latest polls show Mr Rudd's Labor party trailing eight points behind the Liberal-National opposition coalition.
Monday's polls also put opposition leader Tony Abbott - who opposes gay marriage - ahead of Mr Rudd as preferred prime minister for the first time.
Mr Rudd was questioned about the issue by Christian pastor Matt Prater during a live Q&A session.
Mr Prater asked Mr Rudd how he could support gay marriage as a Christian. "If you call yourself a Christian, why don't you believe the words of Jesus in the Bible?" he said.
Mr Rudd responded: "Well mate, if I was going to have that view, the Bible also says that slavery is a natural condition."
"Because St Paul said in the New Testament, slaves be obedient to your masters. And therefore we should have all fought for the Confederacy in the US Civil War."
The fundamental principle of the New Testament was universal love, Mr Rudd added.
"If we get obsessed with a particular definition of that through a form of sexuality, then I think we are missing the centrality of what the Gospel... is all about."
Mr Rudd, who was previously opposed to gay marriage, changed his position in May.
Mr Prater said Christian voters were disillusioned with Mr Rudd "chopping and changing [his] beliefs just to get a popular vote".
However, Mr Rudd said his decision came after a long period of reflection, and was based on his "informed conscience and Christian conscience".
Tony Abbott has described himself as "an opponent of gay marriage", and drew controversy on 14 August when he appeared to describe same-sex marriage as "the fashion of the moment".
Asked about the issue on Tuesday, Mr Abbott said: "Everyone knows where I stand on this."