Lib supporters seem to be drawing some rather interesting conclusions from polling showing that a Lib-only government and a coalition both hold roughly equal support to a Con counterpart. But for the benefit of those who want to see the Harper Cons gone, let's remind ourselves exactly what needs to be done to replace them under the two obvious scenarios available to Michael Ignatieff.
On the one hand, he can keep on trying to run a two-party race based on the message that he'll only take power if the Libs alone exceed the Cons' seat total. In that case, the Libs start from a 12-point deficit based on the 2008 election results, and roughly a 6-point deficit based on current polling. Or put another way, the Libs would need to knock the Cons' level of support down to roughly 32 per cent for there to be any hope of a change in government. Which is no easy task given the Cons' well-documented base of 30% who are firmly in their camp, not to mention the preferences for a Con government in the mid to high 30s.
On the other hand, Ignatieff can send the message that he's willing to work with other parties to replace Harper based on a majority of votes in the House of Commons. In that case, Ignatieff effectively starts from ahead in the race, since both the current Parliament and all available polling leave the Cons with short of a majority on their own. And Harper would then face the need to boost his support level to the 39-40% range to have a chance of holding onto power - which of course reflects the absolute top end of the Cons' recent support levels.
So unlike the choice among parties, this does resolve to a simple either-or choice: the Libs can pursue a message that makes it a near certainty that Harper will be replaced following the next election based on the Cons holding their usual mid-30s vote share, or they can voluntarily set themselves up to lose based on exactly the same voting results. And the fact that they've chosen the latter should cause nothing but reason for suspicion among Canadians who want to see Harper gone.