Pippa Norris, "May's Law of Curvilinear Disparity Revisited: Leaders, Officers, Members and Voters in British Political Parties," Party Politics , 1 (January, 1995), 29-47.

First Paragraph:
A classic issue in studies of party organizations is how we explain party divisions and ideological conflict. Contemporary observers of British politics seeking to understand internal discord commonly focus on particular events, such as power struggles over the role of union affiliates within the Labour conference, or the rise and fall of pro- and anti-European factions within the Conservatives. Others stress broader trends in party popularity, with rumblings of disquiet notably louder during periods in the political wilderness, or with sagging fortunes in the polls. Internal party culture may prove important, with the strongest tradition of loyalty and deference towards the leadership usually (though not always) evident within the Conservative Party, while historically Labour and the Liberal Democrats have more commonly been factionalized. Structural factors provide an alternative explanation, based on the hierarchical lines of power, authority and control within party institutions.

Figures and Tables:
Figure 1: The ideological positions of leaders, sub-leaders and non-leaders according to May's rule.
Table 1: Attitudes toward major welfare issues (%).
Table 2: Attitudes toward major economic issues (%).
Table 3: Attitudes toward social issues (%).
Table 4: Factor analysis of social and political attitudes.
Table 5: Values by party strata.
Figure 2: The attitude structure of Labour and Conservative leaders, members and voters.

Last Paragraph:
As we have found, contrary to May, overall party leaders tend to be more radical than their followers. The most plausible explanation for this pattern is that politicians willing to face the considerable costs and risks of standing for election have to be strongly committed to party principles. The process of campaigning can only reinforce this tendency. If successful, they are immersed in full-time political careers debating in Westminster, defending party policies and working with colleagues from their side of the house. As a result, this experience can be expected to reinforce their initial commitment to such principles as public spending and the provision of welfare, which are seen as fundamental tenets of party faith and which divide British politics.