Introduction In a classic article on the system in Canada, (1968) argued that the single-member plurality system (SMP) for choosing federal Members of Parliament had harmful effects on the party system. The mechanics of this system increased the regional distinctiveness of party caucuses beyond what occurs through social cleavages and voting shares. Since only one candidate can win in a riding, a party with a substantial vote across the constituencies in a region might receive few seats. Thus the party caucuses are more extreme regionally than is justified by voting shares. The system has made a major contribution to the identification of particular sections/provinces with particular parties. It has under-valued the partisan diversity within each section/province. By so doing it has rendered the parliamentary composition of each party less representative of the sectional interests in the political system than is the party electorate from which that representation is derived (Cairns 1968: 62). This is what Weaver (1999) refers to as the Cairns effect. Nevertheless, aside from replying to a criticism of his article in the CJPS (Lovink 1970; 1970), wrote little on this topic subsequently (Cairns 1979; 1981). In April 2001, he submitted a written affidavit in support of the Green Party's suit against the Canadian over SMP under the Charter of Rights and Freedoms. (2) Although Cairns' analysis has been critiqued by other scholars (Lovink 1970; Courtney 1980; Wiseman 1991; 1997), over time it has become increasingly accepted. (3) This has not yet led to a successful reform movement politically, however. The continuing disproportional federal results over the past three elections have been abetted by some strikingly disproportional provincial election results. This has led to more concerted questioning of the system by academics and political activists. Changing the system has managed to secure a tenuous foothold on the formal political agenda in Canada. This paper examines the empirical claims of Cairns' original analysis, their validity during the third of a century since the original article, and why they are having greater impact recently. The Electoral Systems Debate There are several different forms of systems (technically, electoral formulae) in the world. Nevertheless, the most-discussed alternatives are SMP and different versions of proportional representation (PR). In PR systems, seats are distributed on a countrywide or regional basis, and parties rewarded according to their share of the vote in multi-member constituencies. In recent years, mixed systems combining these two systems have made considerable inroads (Shugart and Wattenberg 2001). The ongoing debate between proponents of the two systems traditionally has revolved around the relative priorities of the need for a single party and constituency service versus the accurate representation of voting shares. Strong government advocates see SMP as more likely to produce a with a legislative majority (but not necessarily an overall majority or even a plurality of voters) and one in which there is a direct link between the local constituency and its one representative. PR advocates prefer having a legislature reflecting the partisan distribution of votes more closely, even if that leads to a multiparty formed after the election through negotiations among political leaders. Recent research also has suggested that the form of system may also be an important factor in policy outcomes, irrespective of the partisan coloration of governments (Weaver and Rockman 1993; Lijphart 1994a). did not focus on this broader debate, nor did he advocate a particular alternative formula. Instead, he concentrated on particular disadvantages of SMP for Canada and the general failure to address the issue. …