Who is at "fault" if May does not win her seat?

I'm not a member of any political party (and I'm really not planning to change that) so I've sort of treated the Dion-May alliance/fiasco as a kind of spectator sport (albeit one with potential long-term consequences). Naturally all kinds of opinions have been flying, particularly between Grits and Dippers. My attention was caught today though by something that Jason Cherniak said:

"...if Jack [Layton] were smart he would agree to not run a candidate against Elizabeth May. Then Dion would gain much less from his deal and May would no longer be able to attack the NDP. As things now stand, if May loses and MacKay gets less than 50% of the vote, then Layton will be solely to blame. How many non-partisan progressive voters will like that one? I suspect May understands that she needs to take down #3 before she can even think about Green Party government."

I suppose, given Jason's roll in the Liberal party, he's just doing his job. That said, let me give a response to his rhetorical question about what "non-partisan progressive voters" (like me) would think about May losing Central Nova. First of all, it's one seat. I don't see how Layton would be "solely" to blame anyway. If May runs a mediocre campaign is that Layton's fault? What if the NDP candidate finishes ahead of May, is it then solely May's fault that the NDP lost? Moreover, the NDP never insisted that May run in Central Nova - a riding where the NDP was competitive (at least more so than either the Greens or the Liberals).

Now I don't want to sound like someone who's adopted NDP talking points or anything, so let me just reiterate: I don't think that anyone could point to a single individual and say that they are at fault for an undesirable outcome in an event as complex as a Canadian election.

This is starting to remind me of the bickering liberation fronts in Life of Brian, remember, what the "non-partisan progressive voter" (i.e.: me) wants is for Harper to go away.