5 Things to Know About Ireland's Historic Vote

Ireland's voters decide today whether to legalize gay marriage, with results of the referendum set to be announced tomorrow. While 19 other nations and most US states have already legalized gay marriage, Ireland is the first to hold a national vote. Five things to know:

• Why is Ireland voting? The country's 1937 constitution, written in consultation with Catholic Church leaders, is a document laden with conservative Christian values. Proposed laws deemed at potential odds with that landmark document must be added to the constitution by popular vote.
• What are the Irish voting on? The 34th Amendment of the Constitution (Marriage Equality) Bill 2015. If approved, a new clause would be added to Article 41 of the constitution, which spells out the special rights of the family; it would read: "Marriage may be contracted in accordance with law by two persons without distinction as to their sex." That article previously was amended in 1995 when voters narrowly approved the legalization of divorce.

• Who votes? Any Irish citizen over 18 is eligible and more than 3.2 million are on the electoral register, including 66,000 who barely beat the registration deadline, most of them young people voting for the first time. Polls are open from 7am to 10pm. Thousands of emigrants are flying to Ireland to vote, mostly from neighboring Britain. Arriving flights from London and other British cities are virtually sold out for today, a rarity.
• Which side will win? Eight opinion polls in the past two months of campaigning have recorded a strong lead for "yes" voters. But Irish referendums often produce surprise results, and analysts say several factors could produce a louder-than-expected "no"—so despite the polling picture, "yes" activists express nervousness about the result, while "no" leaders sound confident of an upset.
• What's next? If the verdict is "no," Ireland's gay residents can continue to enter civil partnerships, marriage-style contracts legalized in Ireland in 2010. Advocates of gay marriage could push for another referendum, but that could take more than a decade. If the verdict is "yes," married gay couples will gain constitutional recognition and legal protection as a family unit. No new civil partnerships will be executed, and those already in civil partnerships will have them dissolved if they marry.

Click for more on today's vote. (More Ireland stories.)