I presume this question can eventually be answered by the numbers people. My take is that Harper kept the hardcore vote solid at 30% but could not recruit potential Conservative curious centrists this time. Whether this was primarily a content or style problem is another matter.
Kenney does give good answers which are worth hearing, certainly compared to common PandP performers like James, Calandra or Gill. He had a few missteps in Defence, for example over what a front line is, but he's an excellent performer. One big question is the single man issue. There is no such thing as privacy any more for a leadership contender. Are Conservatives ready for such a situation?