"I'm nervous," said Penny Wong.

With 10 minutes to go before the announcement of the postal survey result, the Labor frontbencher had gathered in front of a TV in a committee room at Parliament House with other Labor, Greens and crossbench MPs.

Wong, known in Canberra for her steely, no-nonsense demeanour, has weathered so much in the years leading up to Wednesday's vote: she was the first openly gay woman in federal Parliament, the first openly gay member of cabinet, who once had to toe the Labor line when her party did not support same-sex marriage.

As debate has raged, she has been forced to defend her family as opponents have compared her two young daughters to a new "stolen generation". She has been told to wait for equality. And wait again.

As the clocked ticked down to 10am, well wishers came up for hugs. Wong took several long drinks of water and joked that it should be straight gin. "I'll sort it out," a staffer suggested.

As the volume on the TV was turned right up and promos played, Wong said, to no one really, "these are the longest minutes of my life".

Then, as the Australian Bureau of Statistics head David Kalisch appeared and the crowd went quiet, Wong bowed her head. "Please be a six [in front of the yes result]."

Tears already forming in her eyes, she quietly prayed.

As Kalisch took his time, running through the tedious process of the vote, the crowd in the committee room guffawed. An impatient Labor senator Sam Dastyari yelled out, "this is Rob Oakeshott!" but Wong did not break her concentration: only giving a small raise of the eyebrows.

Then, at 10:03am, Kalisch announced that 7 million out of 12.7 million people had voted "yes", there was a quick mental calculation. Wong allowed herself a smile. The "yes" vote had won.

When Kalisch clarified this meant 61.6 per cent had voted to legalise gay marriage, Wong put her head in her hands and sobbed.

Immediately, she was bearhugged by colleagues and independent Derryn Hinch placed a rainbow flag on her shoulders. Still, the Labor leader in the Senate kept her head in her hands.

A few minutes later, Wong joked: "I've now cried in front of the whole nation."

When asked how she felt, she said simply: "I'm relieved. Thank you, Australia."

Over in the Coalition-controlled ministerial wing of Parliament House, the tension was palpable as a gathering of pro-change Liberals anxiously waited for the result.

They were in the office of Education Minister Simon Birmingham, a vocal backer of same-sex marriage, who actually missed the entire event because of Senate duties. Instead, Tim Wilson, Kelly O'Dwyer, Trevor Evans and Trent Zimmerman held court. Wilson was joined by his long-term partner Ryan Bolger. The pair have been engaged for eight years and are waiting for the right to marry.

There was a mixture of relief and joy when the number was finally revealed. And a long embrace between Wilson and his fiance.

"This is actually the biggest political mandate in Australian history," Wilson told the crowd.

He, like other "yes" advocates knows there is still a fight to come in Parliament, to make sure same-sex marriage is legalised by Christmas.