New Zealand is expected to become the 13th country in the world to legalise same-sex marriage this evening as a bill to amend marriage law comes before Parliament for its final hurdle.
MPs will debate the biggest change to gay and transgender rights since homosexual law reform 25 years ago, with a historic vote on the third reading of the Marriage Amendment Bill scheduled for around 9pm.
Parliament is likely to back it into law by a wide margin, making New Zealand the first Asia-Pacific country to permit same-sex weddings.
Speaker David Carter has relented on requests from parties on both sides of the House to let more people into Parliament for the final debate.
The legislative chambers will be opened to allow 200 more people to witness it on a large screen.
Hundreds more opponents and supporters are expected to crowd on to Parliament's lawn.
The fully booked public gallery at Parliament will include the Topp Twins, former MPs - including New Zealand's first transsexual MP, Georgina Beyer - the Spanish and French ambassadors and a representative of the US Embassy.
Green MP and rainbow issues spokesman Kevin Hague said it was the most important occasion in his time in Parliament.
"It is truly a historic moment in New Zealand's social and political history. To be part of it is a fantastic opportunity."
He added: "In a few years' time, people will look back on this and wonder what the fuss was about.
"People will not marry their pets. Ministers will not be thrown into prison. People will not be prevented from using the words husband and wife or bride and bridegroom. Teachers won't have any restrictions on what they can teach. And opposition which is based on these fears will melt away."
The Protect Marriage group, led by conservative lobby group Family First, sent out last-minute emails yesterday imploring people to call their MPs and tell them to vote "no".
It provided a list of MPs' phone numbers and said: "Tomorrow is the the day they will try to mess up marriage."
Many opponents of the bill seemed to be accepting defeat.
Former MP Gordon Copeland, who organised a huge prayer vigil at Parliament for the committee stages of the bill, said it no longer appeared that MPs would change their minds.
"There is resignation mixed with a degree of sadness, because I feel that this bill is not in the interests of New Zealand society.
"There will still be an effort in the longer term to resurrect [traditional marriage], but that's for another day, another year."
If the bill passes this evening, same-sex and transgender couples will be able to marry in August.
Gay couples who married overseas will be able to have their marriage officially recognised in New Zealand.
The bill will also have significant impact on transgender communities. At present, married transsexual people are forced to divorce when they change their gender, but they will no longer have to do so if the bill is passed.
The path of the bill into law has appeared certain since it was backed by a two-to-one margin by MPs in August. The legislation was supported by leaders of all parties except New Zealand First's Winston Peters.
Despite a highly emotional select committee process and significant protest from church communities, it lost only four votes of support at the second reading.
The bill's sponsor, Labour MP Louisa Wall, said that despite some scaremongering campaigns, the debate had mostly been respectful, especially when compared with the fuss over the Civil Union Act 10 years ago.
How the parties are split (based on bill's second reading):
* National: 44 per cent of MPs
* Maori: 100 per cent
* United Future: 100 per cent
* Act: 100 per cent
* Labour: 91 per cent
* Green: 100 per cent
* Mana: 100 per cent.
* National: 56 per cent of MPs
* Labour: 9 per cent
* New Zealand First: 100 per cent
* Independent (Brendan Horan): 100 per cent.
Read more: Wall has no marriage plans