When C-14, the Liberal government's legislation to regulate medically assisted death, passed the House at second reading four weeks ago, the vote was 235 in favour, 75 against.

That vote though was likely the easiest C-14 will face. At second reading, MPs are only asked to approve a bill in principle. A member with reservations can vote in favour and hope to see the legislation amended when it goes to a House committee for further study.

On Monday night, with a slightly amended bill reported back to the House, the margin of approval was more than halved, with C-14 passing by a vote of 192 to 129. A series of amendments moved in the House were defeated immediately beforehand.

Just one Liberal and one New Democrat voted nay at second reading, but upon further review, and having seen what amendments the majority was willing to accept, four Liberal MPs voted against, as did all NDP MPs. Still, 19 Conservatives were willing to support the bill, and with those votes on side, C-14 still passed comfortably.

That result suggests the bill will pass again at third reading, a vote that is expected to occur as early as Tuesday evening.

It is at that point that the C-14's margin for passage becomes somewhat mysterious. After passing the House of Commons, C-14 will be delivered to the Senate, an upper chamber in the midst of an experiment in legislative independence.

"The outcome I think is beyond my ability to predict," says Liberal Senate leader James Cowan.

Deadline looms, but criticism mounts

It is seemingly unlikely the Senate will finish with the bill by June 6, the Supreme Court's deadline for new legislation, something Health Minister Jane Philpott seemed to concede on Monday.

"We are at risk of not meeting the June 6th deadline," she said. "Having said that, it is my hope that we can see this piece of legislation put into effect at the very soon as possible date."

The potential impact of any lack of legislation is a matter of some debate, but regardless of when C-14 receives royal assent, it still remains to be seen precisely how, and in what form, it will get there.

Senator James Cowan, Leader of the Liberals in the Senate, says he cannot support the government's assisted-dying legislation in its current form. (Adrian Wyld/Canadian Press)

Among the votes against C-14 on Monday night was that of Liberal MP Rob Oliphant, co-chair of the special committee that was struck late last year to study the Supreme Court's decision on medically assisted death. Oliphant believes the bill is narrower than the Supreme Court allowed for in the case of Carter v. Canada and objects to C-14's requirements that an individual be diagnosed with an "incurable" illness and that death be "reasonably foreseeable."

Those concerns are shared by both New Democrats and the family of Kay Carter and her former lawyer. But also by some of the senators who will soon be charged with reviewing the bill.

An unpredictable Senate

Even beyond the fact that the existing caucuses will likely treat C-14 as a matter of conscience deserving of a free vote, the Senate's 86 occupied seats are currently claimed by a unique mix of senators: 42 Conservatives, 21 Liberals and 23 independents. With the exception of Peter Harder, the government "representative" in the Senate, none have any formal relationship with the Liberal government.

Any proposed amendment must, of course, be accepted by a majority of those 86 senators.

The Senate committee — composed of seven Conservatives, four Liberals and one independent — that completed an expedited study of C-14 earlier this month made several recommendations, some of which dealt with the most contested elements of the bill.

A majority, for instance, recommended providing for advance requests by individuals "diagnosed with a condition that is reasonably likely to cause loss of competence or after a diagnosis of a grievous or irremediable condition but before the suffering becomes intolerable."

But, on the crucial question of eligibility, the committee did not recommend expanding the definition of "grievous and irremediable medical condition." The majority recommended adding "terminal illness" to that section of the bill, while the minority advised deleting the section entirely.

One of the final amendments defeated in the House was a Conservative proposal that would have added language to the bill to provide for consultation about palliative care, an issue raised by a majority on the Senate committee. Three other Conservative proposals, involving conscience rights for medical practitioners, legal review and psychiatric assessment, were supported by a minority on the committee.

If senators do decide to amend C-14, it will be the first time since 2012 that the Senate has sent a bill back to the House. In that case and with another bill in 2009, the House simply agreed with the amendments. If the House disagrees with the Senate's changes, the two chambers can exchange opinions and negotiate. That last occurred in 2006 when the Senate and House took several weeks to agree on the Federal Accountability Act.

In the House, the Liberal government, though criticized from opposite sides, seems to have found enough votes to pass a bill. But it will now be looking for votes in a much different chamber.

Then, in the event of any legal challenge, it will be for the courts to review.