On May 22, Irish voters approved a national referendum on marriage equality. Other countries have legalized same-sex marriage through their parliaments and courts, but Ireland was the first where the public made the decision at the voting booth. This would be an historic moment for any country, but it is even more so for this bastion of conservative Catholicism.
So how did Ireland, one of the last Western democracies to decriminalize homosexuality, become the first country to embrace marriage equality by popular vote? Five factors shaped the outcome.