Raitt or Scheer would perhaps pickup a few points, and at best hold the Liberals to a minority.  They wouldn't embarrass the CPC or its voters by implementing a barbaric practices snitch line or hold a campaign rally with Doug Ford, for instance.  However, I believe they have a low ceiling and would need to hope that the electorate turns against Trudeau in a big way to form a government.  

Mad Max has some interesting ideas (some good, some bad) but is too far out on an ideological branch, in my opinion.  O'Leary would be a disaster.  

The CPC's best opportunities for growth are indeed under Chong or O'Toole.