It's not just the Liberals, the NDP are having a convention this weekend too. Rex shares his thoughts on Tom Mulcair's leadership.

Read a transcript of this Rex Murphy episode

Is the leader of her Majesty's Loyal Opposition on some sort of sabbatical? Has he taken, like certain monastics, a vow of silence, or has he signed on a little too heavily to H.G. Wells’ wonderful fantasy of The Invisible Man?

Now Thomas Mulcair cannot be blamed for the media's fascination with Justin Trudeau, Trudeau is catnip for the cameras. Trudeau, for reasons idle and not idle, fascinates. He's the King of twitter and heir to the most charismatic name in modern Canadian politics.

But Trudeau's "presence" doesn't explain or excuse Mulcair's "absence." Thomas Mulcair has powerful weapons. Opposition leader -- he gets to stare straight across and question Stephen Harper every day.

Mulcair currently owns Quebec federal politics. He faces just a mere rout rump of a third party in numbers. Mr. Mulcair is smart and a good speaker. The Liberals on the other hand have never been so weak and vulnerable as a party. So why is Mr. Mulcair not wielding those weapons?

Well it’s one thing to play the game with a touch of modesty or reserve, but on current conduct it might be fair to ask if Mr. Mulcair is playing the game at all?

Where is he, what is he saying? The biggest news out of the NDP these last few days is one of its members starting a racket about World War I, this is the "socialist" equivalent of one of those famous Clinton "bimbo-eruptions."

The quiet game I once thought Mr. Mulcair was playing is beginning to show as inexplicable passivity -- a leader is morphing into a kind of privileged spectator. Well, no hermit has made it yet, to 24 Sussex.

Meanwhile Justin Trudeau, aiming to lead what is still a broken, diminished, and battered shell of a once mighty machine -- he owns every moment.

Mr. Mulcair's profile is, if anything, less than when he succeeded Jack Layton. His themes are tired: the demon Harper, or contentious and problematic - Dutch disease, or, to my mind, inexplicable - 50 per cent plus one is enough for separation?

There is no sense of fire in the Opposition or its leader, nothing to note that it is (and this is history) the first even NDP national government in waiting. It says a lot that you have to actually remind people of that.

The NDP convention this weekend must flesh out that it really wants to be the government. Debates over whether "socialism" is an acceptable word won't do it.

What are the ideas of the new leader? What does it say to Canadians outside its now huge Quebec base? Why would a Mulcair government necessarily be better than a Harper one?

In sum, Thomas Mulcair has to assert a presence -- claim his place on the stage. It's not sufficient to bemoan Trudeau's appeal.

Party leadership is not a cocoon. Leaders do not follow news, real leaders are news.

For the National, I'm Rex Murphy.