On the federal government's assisted dying bill, the Senate has done precisely what Prime Minister Justin Trudeau wanted it to do: provide independent, non-partisan sober second thought.

But will senators stick to their guns if, as expected, the government rejects their most significant amendment, deleting the requirement that the end of a person's life must already be close in order to qualify for an assisted death?

"Frankly, it's unpredictable," Conservative Senate leader Claude Carignan said in an interview.

A number of different factions, which cross party lines, have developed during debate on Bill C-14, Carignan pointed out:

— Senators who believe the near-death proviso is unconstitutional and that the Senate has a duty to refuse to pass the bill unless and until that provision is removed.

— Senators who think the unelected upper chamber must eventually bow to the will of the elected House of Commons.

— Senators who are morally opposed to the very idea of medical assistance in dying and are likely to vote against the bill, no matter how it is, or is not, amended.

— Senators who believe C-14 is flawed but are likely to conclude that it's better than having no criminal law at all governing assisted dying.

It's possible, Carignan said, that senators with opposing viewpoints will come together for different reasons to defeat the bill — much as happened in 1989, when pro-life and pro-choice senators, for polar opposite reasons, voted against an abortion bill that had narrowly passed the Commons. Canada has been without an abortion law ever since.

"It could happen," he said.

How senators will respond depends to some extent on how the government "manages our amendments," Carignan added, noting that the government ignored the recommendations of the special joint parliamentary committee on assisted dying and the report of the Senate committee that conducted a pre-study of C-14.

"I don't know how many senators will just say, 'Look, that's enough.'"

However, even if the government cavalierly dismisses the Senate's amendments, independent Sen. Frances Lankin said that wouldn't be sufficient reason for senators to dig in their heels and "stray from a reasoned and thorough" response.

"Right now ... I'm leaning towards accepting what comes back from the duly elected Parliament," said Lankin, who voted in favour of deleting the near-death proviso.

While she personally believes the bill is unconstitutional, Lankin said the government vehemently disagrees and legal experts are divided so, ultimately, that will have to be settled by the courts.

The Senate could, she added, urge the government to refer the bill, once passed, to the Supreme Court to test its constitutionality.

As far as Conservative Sen. David Wells is concerned, deleting the near-death requirement is "an important issue but it's not a critical issue." He said he won't insist on it should the government, as expected, reject the amendment.

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