Tom Mulcair practically bounced into our studio yesterday, laughing, teasing and joking in fine form - seemingly without a care or concern in the world.

With his NDP leadership on the line and looking vulnerable, it was either an I-know-something-you-don't swagger of confidence, a worrisome act of delusion or the final acceptance that he might as well go down having some fun.

It's still foolish to predict the outcome of Sunday's Mulcairerendum. The leading antagonists to his continued leadership, be it unions, youth or socialists, don't command total sway over their voting delegates.

A powerful visionary speech by Mulcair just minutes before the voting begins might well overcome the misgivings of the fence sitters.

But snatching a minimum 70 per cent of the convention vote does seem problematic because a surprising number of those who know his leadership the best – specifically current and former MPs - publicly hint and privately confirm their plans to vote for change at the top.

This reflects the real but perhaps misguided belief that the national campaign was the sole reason for the defeat, so that the leader must pay the ultimate price.

The reality is that the fix was in from a Liberal party with better brand strength, a magnetic leader who failed to implode as expected and a platform built on suddenly popular deficits.

It's worth entertaining the possibility that no NDP leader thrust in that scenario could've changed the third-place outcome, including Jack Layton.

Of course, if they dump Mulcair now, the NDP is doing so without an heir apparent for the un-enticing job.

With the exception of charismatic MP Nathan Cullen or an unlikely comeback by former NDP MP Megan Leslie, the leadership gene pool is very shallow.

But if the leader must be the sacrificed to make the party feel better, let the axe fall this weekend.

Nothing saps a party's energy faster than to leave leadership doubts festering as unfinished business.

So if the NDP has any hope of a comeback in 2019, Sunday is the day of unilateral reckoning.

They have to wildly endorse Tom Mulcair, and by that I mean with 75 per cent support or more, or dump him hard enough to eliminate his will to fight on. The mushy middle is political quicksand.

That's the Last Word.