I’m just going to copy Myles’ comment in bulk:

I think this is slightly off: the failure of the Liberals to cooperate with the NDP in bringing down a Harper minority would finally put the lie to the Liberal claim of the last 4 elections: that the only way to save us from Conservative rule was to vote Liberal…and thus would legitimize the NDP as the only true vote against Harper.

I can see why you would (and would want to) believe this, but it genuinely isn’t the case. It’s first important to understand what the Liberal Party of Canada is: i.e., anything but a party of consistent ideological principle. To support a broad-left government in which it is not the leading part is against its nature; it does not recognize such identifications as the “broad left,” because its only political preferences are those which get Canada safely to the next station, decade, century, whatever. It has desire neither for vague idylls of social justice nor fiery claims of moral approbation.

If it supports a NDP government it ceases to have any justification or purpose for existence as an organization and political movement. If the goals of Liberalism is governance by left-wing ideology, why not vote NDP? Why bother having a Liberal Party at all? It’s the mistaken identification of the Liberal Party with the broad left that is silly; the Liberal Party should ‘fess up that it has no principles and its only interests involve getting Canada to the next station, snug and warm, with itself in the driver’s seat. This, rather than some vague incantation of left-wing hopes, is what millions of middle-class Canadian voters vote for. Insofar as Harper was set up as the Liberal bogeyman for electoral purposes, it was because he had a political ideology at all: if the voters found out that his chief interests were sleeping with prostitutes and accepting small-time bribes he probably would get more votes.

So, let’s imagine the unimaginable. If the Liberals support the NDP, what would it mean? It would mean that it seems to subscribe to some sort of political ideology, however vague, rather than just a general lust for power; this is poisonous for the Liberal Party especially, because any affirmation of any kind of ideology is bound to alienate the other half of the party (Blue Grits) who doesn’t subscribe to the particular ideology. It would certainly mean that its broad political identification with the left overrides its destiny as the natural governing party of Canada, and I submit to you that the Liberal Party is absolutely worthless if it is not the natural governing party of Canada, but a generic party of the left, because it is, and has always been, absolutely shit at being a part of the left, even during the Trudeau era. (Pearson never got a majority, not even once.) Basically, it’s turning its entire political purpose on its head; reversing what is important and categorical (natural governing party of Canada) with what is entirely instrumental and supplementary (being of the broad left). I don’t see how the Liberal Party can survive in that condition. Certainly, the Liberals would sustain some damage once the remaining voters who believed that the Liberals actually have any kind of consistent ideology (of the left) are thus disabused of this belief, but I submit that it would be far more than outweighed by the existential damage of self-denial, in completely rejecting the very purpose of the Liberal Party, which is to govern Canada irrespective of ideology or political fashions. I see how a NDP supporter would like to believe the opposite, but that’s just not the case. Jean Chrétien, the most effective Liberal leader in decades, was a complete moral vacuum, and everybody knew it; he had no ideology but the ideology of power, and he had no policy but the policy that which keeps Canada nice enough of a country for it to be worth the bother. Yet he consistently got majority after majority, not because he was some sort of Moses of the broad centre-left, but because he kept the budgets balanced, the economy running along smoothly and nicely, whose chief qualities were that his policies allowed people to go back to their naps.