The assisted dying bill cleared a major hurdle by passing the lower house on Friday.

It was a comfortable margin in the end as the lower house voted 37 to 47 in favour of controversial voluntary euthanasia laws.

But there were times during this long week on Spring Street where it felt much closer than that.

Even as the sun rose on Friday morning and conservative Liberal Robert Clarke continued his rear guard action against the legislation, slugging it out in an epic contest with Health Minister Jill Hennessy, there were those who feared the member for Box Hill might continue to fight these reforms another day.

But for many who sat through the gruelling days of emotional debate, beginning on Tuesday and culminating in a final conscience vote on Friday morning after a marathon 25 hours in the chamber and a sleepless night, this was parliamentary democracy at its best.

Here were politicians putting belief and principle above party loyalty and even personal comfort and convenience, telling deeply intimate and sometimes heartbreaking stories, while debating a difficult and divisive social reform.

It was a week to restore some of the battered faith in our democratic institutions, although the "filibustering" and sleep-depriving tactics of the leading opponents eventually led many MPs to take issue with the ultimately futile attempts to prevent a vote on the bill this week.

The Andrews' government started on Tuesday quietly confident it could get its bill through. The government was even hopeful it could be done by Thursday, perhaps not paying enough attention to Mr Clark's notice of amendments and his determination to resist what he believed was a deeply flawed bill.

But the first sign of real trouble came from a different but not wholly unexpected source: Deputy Premier James Merlino, a devout Catholic and longstanding, vocal opponent of the voluntary assisted dying legislation.

Mr Merlino's "reasoned amendment", essentially a series of conditions that would put the whole legislative process on indefinite hold, sent the government into a spin when he unveiled it before a vote on Wednesday evening.

The motion was easily defeated on the floor of the house. But the lively little squabble over Mr Merlino's ambush could leave scratches in the Labor caucus that will take time to heal. Not least Ms Hennessy's text message which she inadvertently sent to him at the height of the crisis on Wednesday night calling her cabinet colleague a c**t.

With Mr Merlino's amendment disposed of, and the Labor hierarchy's confidence buoyed by the comfortable 49 to 36 assent of the bill's second reading, government figures prepared for a long but ultimately successful day on Thursday.

It started off as planned, with the bill due to go to the "committee stage" but when more than 330 amendments to the legislation appeared on the notice paper on Thursday morning, the full extent of what the opponents of the bill had planned began to crystalise.

Some of the amendments, like tighter controls on doctors' advertising euthanasia services or more comprehensive collection of data on instances of assisted dying, were acknowledged to be worthy of debate.

But others, such as referring to the lethal medication to be used to end the life of a terminally ill patient as "poison", looked simply provocative and invited accusations that a group of MPs around Mr Clark were simply filibustering.

Thursday afternoon brought another last minute intervention, former Prime Minister Paul Keating proving his genius for political theatre was still intact with a plea published on Fairfax websites for MPs not to go through with a yes vote.

But Keating's gesture, while dramatic, was never likely to sway the votes of a group of politicians who had been studying this matter in depth for more than two years,

As Thursday afternoon turned to evening, there were plenty of dissenters, including Labor frontbencher Marlene Kairouz and backbencher Lizzie Blandthorn, arguing in vain for changes to the bill with amendment after amendment being knocked down.

But as the night wore on into the small hours, the band of fighters dwindled with Mr Clark, supported by fellow Liberals Murray Thompson and Graham Watt still refusing to bow to the inevitable.

"Our resolve is strong," a watching government official said as the sun came up.

"We're not going to blink."

Neither Mr Thompson nor Mr Watt fell silent, but by mid-morning it was the battle of wills between Mr Clark and Ms Hennessy that seemed to fill the chamber with most of their colleagues clearly wilted around them.

Just after 10am, after more than 24 hours, exhausted MPs began streaming back into the chamber, sensing the end was near with even Mr Clark now unable to delay the inevitable any longer.

Ms Hennessy paused to pay tribute to her "indefatigable" adversary.

It was a big moment.

After all of that, the response to the bill's passage was a little muted, perhaps with the 87 MPs utterly spent after their long days and nights.

Now the bill must go to the upper house, where many supporters believe they have the numbers. But nothing is guaranteed.

"This week we have seen incredibly powerful contributions from all sides of the debate as Members of Parliament have shared their personal experiences and given this issue the consideration it deserves," Hennessy said.