The obvious candidates, from amongst sitting MPs, are:
Rona Ambrose, Jason Kenney, Kellie Leitch, Erin O’Toole, Lisa Raitt and Michel Rempel ~ all minister in the last government.
Two recently retired ministers might, also, be drafted back into the contest:
Peter MacKay and John Baird.
I think Maxime Bernier will be in the race, but cannot win:
I would call Jason Kenney the front runner, but I think Dr Leitch might be a formidable challenger.
The good news is that the CPC has an embarrassment of riches in terms of potential leaders.