The Irish voted on Friday on whether to allow gay marriage, just two decades after Ireland became the last country in Western Europe to decriminalize homosexuality.
With the once mighty Catholic Church's influence ravaged by child abuse scandals, opinion polls indicated the proposal would pass by as much as two-to-one, making Ireland the first country to adopt same-sex marriage via a popular vote.
Enormous international interest made the hashtag #VoteYes the top trending issue on Twitter and thousands of Irish expatriates made the trip home from Britain and as far afield as New York and Sydney to vote, groups encouraging the 'Yes' vote, using the hashtag #hometovote, said.
"I voted 'Yes' because everyone's the same so why not have the same rights as everyone else," said Dubliner Jennifer Brown, 21, who voted on her way to a university exam.
"Surprisingly some of my friends are against it but the ones who say they are going to vote 'No' aren't going to actually vote."
The result may depend on whether younger voters, tens of thousands of whom registered as the campaign gathered momentum, actually turn out to cast their ballots.
Results, which will be declared on Saturday, may also reveal an urban/rural split. When voters legalized divorce by a razor thin majority in 1995, only five of the 30 constituencies outside Dublin backed the proposal.
Gay marriage is backed by all political parties, championed by big employers and endorsed by celebrities, all hoping it will mark a transformation in a country that was long regarded as one of the most socially conservative in Western Europe.
The Catholic Church, whose doctrine teaches that homosexuality is a sin, has mainly limited its 'No' campaigning to sermons to its remaining flock, a marked contrast with active public opposition to similar moves in France and elsewhere.
Instead, lay groups have led the opposition, raising concerns over parenthood and surrogacy rights for gay couples. Many believe the recognition of the legal rights of same-sex couples in 2009 is sufficient.
"I don't think it's necessary because it's covered in the civil partnership arrangements," said Sean, a retiree voting in the leafy Dublin suburb of Blackrock. Only a couple of his friends were voting 'Yes', he said.
"I'm not convinced, I think it's wrong and I don't agree with it."
