Which isn't to say that I'd see Mulcair's campaign as entirely running against the NDP's existing legacy. But he's certainly making statements which seem far more likely to serve as fodder for future Con ads than as reasonable descriptions of where the NDP stands at the moment:
"If we continue to say what we should spend money on without saying where we will get money from, then I think that the public might look at us and say, 'Well, we don't think that you are going to be able to do this job.'Of course, one could see the issue as simply a divergence of interests between Mulcair and the broader party if the effect of such a message was to help his cause in the leadership race. But the more important problem for Mulcair is that he looks to have opened up about the widest possible pathway for Brian Topp to claim the leadership.
"So the trick for us is to convince Canadians that we can and do have a team of men and women who can manage the public purse in the public interest and keep things on target with regard to budget and administration."
It was one thing for Topp to have the advantage of being the establishment candidate, which to my mind only countered his disadvantage in not yet being an elected MP. But if Topp can position himself as both the choice of the NDP's operational core assembled by Jack Layton and the defender of left-wing values within the leadership campaign (which a few weeks ago would have seemed highly implausible for a candidate known in large part for his association with Roy Romanow's government), then it's hard to see a path to victory for any other candidate that doesn't involve bringing in tens upon tens of thousands of new members from outside the party.
Naturally, the calculus could change if another candidate does move into the ample room on the left. But it's far from clear who might be able to mount a challenge on that front. Of the candidates currently in the race, Romeo Saganash is the only one who hasn't positioned himself primarily as a centrist - meaning that his odds of joining the perceived top tier of candidates may soar if the field remains as it stands. Or alternatively, it could be that a Peggy Nash or Niki Ashton will jump into the race with a more progressive message than that being delivered by the candidates so far.
Moreover, while the development of a third top-tier candidate to push the race leftward might reduce the likelihood of a first-ballot romp for Topp, it wouldn't figure to do a lot of good for Mulcair if he spends the leadership race alienating the more progressive voters who get drawn into the race by that campaign - at least barring a complete reversal of fortune for Topp that forces his supporters to split off between Mulcair and the new challenger on a final ballot.
As Silver notes, then, it's curious to see Mulcair so eagerly cut himself off from much of the NDP's existing base at the outset of the leadership campaign. And the result may be to make Topp much more of a favourite than seemed possible not long ago.