In spite of the fact that the Greens haven't elected any MPs to seats, they have run numbers in the 5-8% range in the last two elections - more than enough base support to demonstrate that there is a significant amount of interest in what they have to say.
There have been many times in the past when the NDP in particular has been polling down in that same range. Which is one of the reasons I take exception to the argument that 'only people who have a chance of becoming PM should be in the debate' that has been put forward. This is a spurious argument, IMO, because it suggests that only two leaders should ever be in these debates - the incumbent PM and the Leader of the Opposition. (Historically, I don't think that the 'third party' leaders have ever prevailed on election day)
But, what really bothers me about this whole affair is the way that Harper and Layton have been moving in virtual lock-step with each other on this:
The broadcasters changed course after Conservative Leader Stephen Harper and NDP Leader Jack Layton indicated earlier Wednesday that they no longer oppose May's participation in the debates on Oct. 1 and Oct. 2.
... and just a few days ago, we have this:
In arguing against May's inclusion, the Tories and NDP cited a deal she struck with Dion, in which they agreed not to run candidates against each other in their respective Nova Scotia and Quebec ridings.
It strikes me that Msrs. Harper and Layton are cut from the same Machiavellian cloth - it's all about personal gain for them, not about making Canada a better place to live.