DUBLIN - Irish voters backed same-sex marriage by a landslide in a referendum marking a dramatic social shift in the traditionally Catholic country, government ministers and opponents of the bill said on Saturday.Final results were not expected until later in the day, but ministers predicted Ireland had become the first country to adopt same-sex marriage via a popular vote by a margin of around two-to-one, just two decades after it decriminalized homosexuality."This has really touched a nerve in Ireland," Equality Minister Aodhan O'Riordain said at the main count center in Dublin. "It's a very strong message to every LGBT (lesbian, gay, bisexual, and transgender) young person in Ireland and every LGBT young person in the world."Health Minister Leo Varadkar, who revealed he was gay in a radio interview in January, said the referendum resembled a "social revolution."The proposal was backed by all political parties, championed by big employers and endorsed by celebrities, all hoping it would mark a transformation in a country that was long regarded as one of the most socially conservative in Western Europe.Only a third of the country backed the decriminalization of gay sex for men over 17 in 1993, according to a poll at the time. A supreme court judge in 1983 said homosexuality was "morally wrong" and contributed to depression and suicide.