Maurice Duverger is arguably the most distinguished French political
scientist of the last century, but his major impact has, strangely
enough, been largely in the English-speaking world. His book, Political
Parties, first translated into English in 1954, has been very
influential in both the party politics literature (which continues to
make use of his typology of party organization) and in the electoral
systems literature. His chief contributions there deal with what have
come to be called in his honor Duverger's Law and Duverger's Hypothesis.
The first argues that countries with plurality-based electoral methods
will tend to become two-party systems; the second argues that countries
using proportional representation (PR) methods will tend to become
multi-party systems. Duverger also identifies specific mechanisms that
will produce these effects, conventionally referred to as "mechanical
effects", and "psychological effects". However, while Duverger's
Hypothesis concerning the link between PR and multipartism is now widely
accepted; the empirical evidence that plurality voting results in
two-party systems is remarkably weak-with the U.S. the most notable
exception.
The chapters in this volume consider national-level evidence for the
operation of Duverger's law in the world's largest, longest-lived and
most successful democracies of Britain, Canada, India and the United
States. One set of papers involves looking at the overall evidence for
Duverger's Law in these countries; the other set deals with evidence for
the mechanical and incentive effects predicted by Duverger. The result
is an incisive analysis of electoral and party dynamics.
