HInt; they are likely to listen if they know you can fire 'em.

Something you don't see often: sense from a parliamentarian on the problem with making party leaders accountable to no one:

The primary system would give the Liberal leader and his/her office more power over Caucus and the Party. As a recent Member of Parliament with almost 18 years of experience, I can say with first-hand knowledge, that, most of the time caucus is not considered or listened to by the leader and especially his office. There is very little accountability to caucus members. Especially during our years in opposition, we could have avoided a great deal of pain and losses if the leadership and their offices had listened and taken into consideration the expertise and advice of caucus members. Therefore, I am convinced that a Leader who is so broadly elected will feel even less accountable towards caucus let alone any accountability to the party at large.

The comment is from former Liberal MP Maria Minna.  The Liberal convention did not approve the proposal to elect future leaders by mass public primary voting.  Credit to Aaron Wherry's blog at Maclean's, which made Minna's letter available.