....In 1965, we find only two methods of leadership choice in use: selection by the parliamentary caucus and by a delegate convention. Selection by parliamentary caucus is consistent with traditional notions of parliamentary government in which the party leader’s primary task was to captain the parliamentary team. In many parties, the party leader was not yet dominant outside the parliamentary caucus and in some cases was not even formally in charge of the extra parliamentary party. The aggregate numbers mask the strength of the parliamentary party in leadership selection at this time. In four of our six countries, Australia, Ireland, New Zealand and the United Kingdom, all of the parties in our sample chose their leaders through a vote of MPs in 1965. The Canadian and Belgian parties were the exception. The Canadian parties abandoned caucus selection in favour of delegated conventions by the 1920s. The Belgian parties, for their part, never gave the caucus the formal authority to select the president but this may be due to the fact that the president initially did not have much power and, perhaps most importantly in contrast with the Westminster party systems, the president was not the leader of the parliamentary party.
By 2007, the proportion of parties in which the parliamentary caucus makes the choice by itself has dropped from two thirds to one quarter of our sample and this aggregate number is inflated by the continued popularity of this method in Australia and New Zealand. All three of the major Australian parties continue with caucus selection as do the largest New Zealand parties. Only one party in our sample outside of these two countries continues to choose its leader exclusively through a vote of its parliamentary caucus - Ireland’s Fianna Fail.....
