Party leaders are chosen by the membership, through their local delegates at convention.
The party members determine the leader, and the MP's are chosen by the people. When
someone runs for a political party they are subscribing to the policy of the party and that
is how the system works. If the party takes a position on a particular measure and you are
a member of that party, if you vote otherwise you can be booted out of caucus and so it
should be. People have to know the policies of the party they represent and the public has
to know the direction of the person they are voting for.
I personally think the system works well. When I ran in 1997, I agreed with most of the
policy issues of the day but not all that would be impossible. The party I represented at the
time was in favor of gun control, and I am not and said so. Had I been elected I would have
faced some difficulty personally, as the policy is for gun control and personally I think it is
self serving. Its a giant waste of money for one and no one has ever been spared because
of gun control, in fact I think it creates a false sense of security.
On topic here, the party leaders have only the power the membership gives them, and that
also goes for the Member of Parliament. There have been cases where the member did not
get party support at nomination time and in turn leaders have been sacked by their membership.
Gordon Campbell knew the full membership would have dumped him and Carol James would
have met the same fate had there been a convention. I think there is a good balance of power
and checks and balances.