One of the chief tasks facing political leaders is to build and maintain unity within their parties. This text examines the relationship between party leaders and Members of Parliament in Britain, Canada, Australia, and New Zealand, showing how the two sides interact and sometimes clash. Christopher J. Kam demonstrates how incentives for MPs to dissent from their parties have been amplified by a process of partisan dealignment that has created electorates of non-partisan voters who reward shows of political independence. Party leaders therefore rely on a mixture of strategies to offset these electoral pressures, from offering MPs advancement to threatening discipline, and ultimately relying on a long-run process of socialization to temper their MPs' dissension. Kam reveals the underlying structure of party unity in modern Westminster parliamentary politics, and drives home the point that social norms and socialization reinforce rather than displace appeals to MPs' self-interest.

A model of policy implementation in a parliamentary democracy as delegation between the prime minister and her cabinet ministers is introduced. Cabinet reshuffles can be pursued as a strategy to reduce the agency loss which occurs due to the different preferences of the actors. This work thus explains why prime ministers resort to reshuffles: cabinet reshuffles reduce the moral hazard facing ministers. This answer both augments and distinguishes this work from traditional perspectives on reshuffles that have emphasized the deleterious effects of reshuffles on ministerial capacity, and also from recent work that casts reshuffles as solutions to the adverse-selection problems inherent in cabinet government. The conclusion offers a preliminary test of some of the hypotheses generated by this theory.

T his article promotes a characterization of intraparty politics that explains how rank-and-file party members control the delegation of power to their cabinet ministers and shadow cabinet ministers. Using the uncovered set as a solution concept and a measure of party members' collective preferences, we explore the hypothesis that backbenchers' preferences constrain the ministerial selection process in a manner that mitigates agency problems. Specifically, promotion is distributed preferentially to members whose own policy preferences are proximate to the uncovered set of all party members' preferences. Our analysis of ministerial appointments in the contemporary British Parliament supports this view. For both the Labour and Conservative parties, front bench appointments are more sensitive to the collective preferences of backbenchers in each party as measured by the party uncovered set than to the preferences of the parties' leaders.

Despite their political prominence, cabinet reshuffles have not attracted a great deal of scholarly attention. We provide a theory of cabinet reshuffles that emphasizes both systematic and time-varying causes. In particular, we argue that prime ministers employ cabinet reshuffles to retain power in the face of both intraparty and electoral challenges to their leadership. We use repeated-events duration models to examine the timing of cabinet reshuffles in Australia, Canada, Ireland, New Zealand, and the United Kingdom in the period 1960-2001, and find support for several of our hypotheses.Christopher Kam and Indriði Indriðason Q: Why does the PM not simply change one underperformer at a time rather than making these broader midterm changes? There is organizational stability to think about, after all.A: Well, let me give you an example. In our first Parliament, David Collenette gets into trouble-he called a judge or something about a case-and our tradition here is that when something like that happens, the minister resigns, and David did. Now, at the time, he held the defense portfolio, a major portfolio. So, now this creates two problems. First, do you pull a rookie up from the backbench and put them into a major portfolio? Or do you move a veteran into the defense portfolio and give the rookie a minor portfolio? And don't forget that the PM has to deal with all sorts of restrictions: he has to make sure that all provinces have a minister, and then there's the relative importance of a particular portfolio to certain regions.