MONTREAL — Can anyone imagine a defeated Stephen Harper returning to the House of Commons at this time next year to ask questions of Prime Minister Justin Trudeau or Thomas Mulcair?

Don’t court a brain cramp by considering the prospect for it is not in the cards.

According to polls, a Conservative defeat next year is well within the realm of possibility, but Parliament watchers agree that in such circumstances Harper would not stick around long enough to critique the new government’s first speech from the throne.

But would Harper — if he won — actually stay on to run another minority government?

Would the opposition even allow him to remain in office for any significant length of time?

Would Mulcair have the fortitude to lead the NDP from third place in the House of Commons?

And is Trudeau’s leadership really bulletproof no matter how his party does next year?

The answers to all these questions are less obvious than they may seem at first glance.

Take Trudeau. The rookie leader combines the dual status of Liberal favourite son and potential saviour. Almost to a person, Liberals will swear that they are behind him for the long haul. For the first time in decades, they do not have a substitute leader waiting impatiently in the wings for the current one to stumble.

Many Liberals hope the party will vault from third to first place next year. But most would consider it a job decently done if Trudeau finished a strong second.

Bringing the party back from third place to the major leagues is job one for the Liberal leader. But what if that does not happen? Patience with a losing leader has never part of his party’s culture.

The federal NDP on the other hand does have a history of sticking with a leader for more than one campaign. Audrey McLaughlin was a recent exception but her first and only campaign in 1993 saw the NDP reduced to nine seats.

No one expects a repeat of that disaster under Mulcair but the real test of his leadership will involve doing as well or better than Jack Layton did four years ago.

At a minimum that would require leading the NDP to a strong second place across Canada and finishing first again in Quebec.

At year’s end neither is guaranteed. There has not been a national poll that has placed the NDP in better than third place for almost two years. And while the party remains strong in Quebec it is vulnerable on a number of flanks.

It would not, for instance, take a huge Bloc Québécois resurgence for splits to result in NDP seats falling onto the Liberal lap.

Mulcair does not lack for critics within his own party. He was not the preferred choice of a significant part of the NDP establishment. His performance in the Commons and the party’s staying power so far in Quebec have driven those critics underground. But should the New Democrats fall back to third place and/or do poorly in Quebec next year, the knives could be out quickly for this particular leader.

And then Mulcair is a proud man. No one can assume that he would be more keen to play the role of second opposition fiddle in the next mandate than Harper would be to trade government for opposition.

But how would the prime minister feel about trading a Conservative majority for another minority? He knows first hand that the powers of a minority prime minister are ultimately only slightly less extensive than those of a majority one.

But Harper earned his previous minority mandates on the way up to a majority. Should it slip away next fall it would be the first time the Conservative party lost ground under his leadership. Such a result would take a toll on his authority over the party and the caucus.

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Harper himself maintains and probably believes that if the Conservatives fall short of a majority next year, the opposition parties will — this time around — get their act together and come to an arrangement to replace his party in power.

That is not necessarily a given. But more on that in an upcoming column.

Chantal Hébert is a national affairs writer. Her column appears Tuesday, Thursday and Saturday.

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