They just don't know when to quit
So why open up the can of worms in the first place? There are two possibilities, and they're related. The first possibility is that Harper is feeling some heat from the radical neo-con part of his party to ramp up the agenda and fast or lose the support of the base. It's not like the neo-con part of the Conservative party hasn't broken off in the past and started anew. Now Harper can read the polls as well as the rest of us and knows that to placate the base, he has to scare off the vast majority of Canadians. So he can't openly call for the death penalty. So he has to do it through the back door, reversing decades of Canadian Government policy both with respect to the US, the only western democracy with the death penalty, or in the UN, a body most neo-cons have nothing for contempt for in the first place. With this Harper can show the base that he's getting "tough on crime" all the while putting a facade forward that he doesn't want the death penalty debate reopened.
Note how he said he didn't want the debate reopened and not that he didn't want the death penalty reinstated. A clever non-answer to the direct question of do you want to bring back the death penalty. This leads to the second possibility. Harper isn't trying to play to the neo-con faction, but is in fact deep in it and is just waiting for his coveted majority to spring the death penalty on Canadians. With a majority government Harper wouldn't have to have the messy debate that he'd have to have with a minority government. He could just ram legislation through the house with little debate and viola, instant death penalty in Canada. It's not like he'd allow any dissent in his caucus. It all comes back to the so-called hidden agenda. If there's no hidden agenda, as Harper likes to posit, then the actions of his government vis-a-vis the death penalty outside of Canada are contradicting this. If there is a hidden agenda, the way the Harper government is acting is telegraphing that agenda, making it less hidden of course.
The danger for Harper in all this is that the death penalty issue sticks. This won't gain them votes anywhere in Canada and is likely to cost votes, especially in areas like Quebec and Ontario where Harper desperately needs them. One wonders why he is embarking on this dangerous strategy. There's really no need for Harper to pander to the base, as there isn't really any danger of them going somewhere else, there being nowhere for them to go. Outside of Harper's base of support, the number of people who would support a return of the death penalty are few and far between, making these moves even more curious from a domestic politics point of view. The best thing the opposition can do right now is keep on the Harper government on this topic, make the issue stick to the Tories like so much manure. This issue will do nothing but hurt Harper.