Yes, it's inevitable that Tom Mulcair will have to answer the Cons' (however farcical) talking points about some nonexistent carbon tax. But there's more to the story than the "big lie" currently being pointed out by Mulcair - and the best way to turn the issue back around on the Cons is to take them at their word from four years ago.
After all, the Cons' commitment to a cap-and-trade system in 2008 doesn't just make them hypocrites for bashing the same idea now. Instead, it also looms as a massive broken promise in an area where the Cons have so often gone out of their way to prove they can't be trusted. And it also serves as a signal as to what the Cons really value rather than the best interests of Canadians.
Yes, Harper has pretended to agree with greenhouse gas emission regulation for the purpose of deflecting from the environment as an election issue. But he's only been willing to feign support for whatever policy seems furthest from being implemented - with the apparent goal of making sure that no single form of regulation gains enough momentum to be seen as an inescapable consensus.
Moreover, in government Harper has consistently refused to implement any policy which actually results in the oil sector (rather than the general public) taking responsibility for the damage unregulated greenhouse gas emissions can do to Canada's environment and the global climate. And the fact that a majority Con government is managing to be even more reckless than the previous minority versions only drives that point home.
So the real story isn't merely that the Cons are lying - it's that they're lying in service to their tar-sands masters, and will say or do anything to ensure a continued flow of wealth from the Canadian public to oil barons. And the best way to highlight that lie is to focus on asking when the Cons will get around to making good on their 2008 promise - and forcing them to argue against their own words and platform.