He maybe isn't the best choice for the Conservatives but not the worst either.  Leitch, Blaney, Trost, and O'Leary (if he enters) are the worst and choosing any of them would risk the party falling to third place.  Scheer is conservative enough it would make it very difficult for them to win in 2019 unless Trudeau messes up badly, but also moderate enough they would likely still maintain official opposition status.  Chong and Raitt are the only ones that might have a shot at defeating Trudeau, but at least either of those two would probably improve the Tory seat count even if they fall a bit short.