While Harper was PM, it was politically useful for opponents to ascribe all policy to him; indeed, he cultivated that (“the Harper government”). It hid the body of Conservative support somewhat, which helped focus opposition.
However, now that he’s resigned, it strikes me as much more useful to talk about those same policies as Conservative party policies instead: raise the profiles on the ministers who enacted them; don’t let them escape their actions through amnesia. Remind everyone that it wasn’t one man, it was a plurality that all believed that. Rona Ambrose shows signs (sensibly!) of wanting to distance the party from Harper: don’t let that happen. They’re all responsible for what I’m already starting to thing of as “Canada’s Lost Decade”