To these
socio-economic and historical factors a technical factor
must be added: the electoral system. I expressed its
effects in 1946 in the formulation of three sociological
laws: (1) a majority vote on one ballot is conducive to a
two-party system; (2) proportional representation is
conducive to a multiparty system; (3) a majority vote on
two ballots is conducive to a multiparty system, inclined
toward forming coalitions. The brutal
finality of a majority vote on a single ballot forces
parties with similar tendencies to regroup their forces
at the risk of being overwhelmingly defeated. Let us
assume an election district in which 100,000 voters with
moderate views are opposed by 80,000 communist voters. If
the moderates are divided into two parties, the communist
candidate may well win the election; should one of his
opponents receive more than 20,000 votes, the other will
be left with less than 80,000, thereby insuring the
election of the communist. In the following election, the
two parties with moderate views will naturally tend to
unite. Should they fail to do so, the weaker party would
gradually be eliminated as a dual consequence of
"under-representation" and "polarization." Under
representation is a mechanical phenomenon. Elections
determined by a majority vote on one ballot literally
pulverize third parties (and would do worse to fourth or
fifth parties, if there were any; but none exist for this
very reason). Even when a single ballot system operates
with only two parties, the one that wins is favored, and
the other suffers. The first one is over-represented--its
proportion of seats is greater than its percentage of the
votes-while the party that finishes second is usually
under-represented--its proportion of seats is smaller
than its percentage of the votes. The English, with their
two-party system, have expressed this phenomenon by the
law of the cube: the relationship in the percentage of
seats held by the two parties would be equal to the
relationship of the cubes of the percentages of the votes
received (if a and b are the percentages of
the votes, and a' and b' the percentages of
the seats, then we find that a' / b' = a3 /
b3). When there
is a third party, it is even more under-represented than
the second. The gap is generally quite large, with the
proportion of seats far below the proportion of the votes
received. In 1964, the British Liberal party received
11.2 per cent of the votes cast, but only 1.4 per cent of
the parliamentary seats. This under-representation tends
to eliminate the effects of any votes cast for a third
party. But voters are aware of this phenomenon. They also
know that a division of votes between two parties holding
similar views favors their common adversary. In the case
mentioned before, the moderate voters would see clearly
that a split between the moderate candidates guarantees a
Communist victory: in a subsequent election they would
drop the weaker of the two moderate candidates. Thus it
is that voters tend to abandon the third party in order
to concentrate their votes on the two strongest parties.
This tendency toward polarization, a psychological
phenomenon, strengthens the mechanical factors conducive
to a two-party system. In a system
of proportional representation, the situation is quite
different. The very principle of proportional
representation explains the multiplicity of parties it
produces. Since every minority, no matter how weak it may
be, is assured of representation in the legislature,
nothing prevents the formation of splinter parties, often
separated only by mere shades of opinion. If the
conservative party has 6 million votes in the country,
corresponding to 300 seats in parliament, and if it
splits into three groups about equal in numbers,
proportional representation will give each of these about
a hundred deputies, and the conservative family will have
the same strength in parliament. In other respects, this
electoral system does not encourage parties to unite. A
coalition is useless from an electoral point of view
since the entire system tends to permit everyone to take
his chances at the polls.,Hence the reciprocal
independence of the political parties. In a system
in which elections arc decided by a majority vote on the
second of two ballots, political parties are numerous
because the existence of a second ballot permits each
party to test its chances on the first one without
risking irrevocable defeat through the splintering of
parties holding similar views; the regrouping occurs on
the second ballot through the game of "withdrawals." Let
us again use the illustration of an election district in
which the conservatives have 100,000 voters and the
communists, 80,000. If the conservative electorate
divides into two parties, with the first receiving 60,000
votes and the second, 40,000, while the communists vote
as a bloc on the first ballot, there will still be a
second ballot. For the second round, the weaker
conservative candidate will withdraw. His supporters will
switch their votes to the stronger candidate, who will
normally be elected. New parties can thus multiply, but
they are usually driven to form alliances with one
another to check their opponents by means of "retreats"
and "withdrawals." The second ballot is essentially a
voting by coalitions, as was seen in France during the
Third Republic and in Imperial Germany, the two large
countries that have practiced this system. Although
the preceding laws have been much discussed, often in
heated debate, they have never been seriously challenged.
The criticism directed against them has not questioned
the reality of the phenomenon they express, which is
fairly obvious, as much as the precise extent of its
influence. It is clear that an electoral reform by itself
will not create new parties: parties are a reflection of
social forces; they are not born of a simple legislative
decision. We can be sure that the relationship between
electoral systems and party systems is not something
mechanical and automatic. A given electoral regime does
not necessarily produce a given party system; it simply
exerts an influence in the direction of a particular type
of system; it is a force, acting in the midst of other
forces, some of which move in an opposite direction. It
is also clear that the relationship between electoral and
party systems is not a one-way phenomenon; if a
one-ballot vote tends toward a two-party system, a two
party system also favors the adoption of a single ballot
voting system. The exact
role of the electoral system seems, in the last analysis,
to be that of an accelerator or that of a brake. An
election by a majority vote on a single ballot has a dual
effect: first, it poses an obstacle to the appearance of
a new party, although this obstacle is not insurmountable
(the role of a brake); secondly, it tends to eliminate
the weakest party (or parties) if there are more than two
(the role of an accelerator). The braking effect was
noticeable in Great Britain at the end of the nineteenth
century, in the face of a socialist drive, and again
after World War 1, in the face of communist and fascist
movements. The accelerating effect was even more apparent
in the case of the Liberal party, which was practically
eliminated in fifteen years (1920-35), although it
retains a certain number of supporters who are compelled
by the electoral system to choose between Conservatives
and Labourites. Deciding by a majority vote on one ballot
accelerated in Great Britain the substitution of a
two-party system for any other kind. Proportional
representation plays just the opposite role. It does not
slow down the development of new parties. It passively
registers their appearance, sometimes amplifying the
vibrations they generate, like an echo chamber or a
seismograph. (In order to check this tendency,
proportional representation is rarely applied in toto;
it is modified by such measures as permitting local
districts to apportion residual votes and by establishing
rules regarding the percentage of votes required to gain
representation in the legislative assembly.) On the other
hand, it retards the elimination of old parties which
would otherwise tend to disappear as the social and
political scene changes. The "salvaging" of the Belgian
Liberal party through proportional representation,
beginning in 1900, is a typical example of this
phenomenon. Instead of giving way to a
twentieth-century-style two-party system, the
nineteenth-century system survived with the new system
superimposed on it, producing an essentially three-party
system (this was also the case in Germany and Austria),
However, we must of course distinguish between old
movements, deeply rooted among a portion of the
population, and superficial movements reflecting
temporary political moods or fashions. Proportional
representation registers just as clearly the appearance
as it does the disappearance of parties of this latter
type. Typical examples were the case of "rexism" in
Belgium, and, in France, the RPF [Rassemblement du
Peuple Francais] in 1951, and Poujadism in
1956. The results
of the two-ballot majority system are similar to those of
proportional representation, with a few differences. The
two-ballot system seems to be more discouraging to the
formation of new parties than proportional representation
(but it is far less effective in this than the
single-ballot majority vote). Perhaps it is also more
helpful to older parties with party leader Dr. Fehsenfeld, but it is difficult to
formulate any definite conclusions in this matter.
Furthermore, it seems to present a certain barrier to
brusque changes of political opinion, to movements
reflecting momentary moods or impulses, to political
groups that are "fashionable" but ephemeral (even though
the example of the UNR [Union Nouvelle pour la
Republique, the Gaullist party] in 1958 proved to
be of a different kind: but the circumstances in this
instance were very special). The sharpest difference with
the system of proportional representation concerns
electoral alliances, A coalition system par excellence,
the two ballot regime can sometimes permit the formation
of a dual system of alliances, introducing a sort of
two-party system in the midst of a multi-party situation.
This phenomenon was quite evident in France during the
Third and the Fifth Republics, and in Germany from 1870
to 1914. Having said
all this, the fact remains that a change in the electoral
system does not always have a decisive influence on the
existing party system. However, it seems certain that if
proportional representation were to replace the majority
vote in Great Britain, a three-party system would appear
before very long, making party splits within the ranks of
the Labourites and the Conservatives much more likely.
The influence of a one-ballot vote in maintaining an
already established two-party system is beyond question.
It is much less certain that the adoption of such an
electoral system would destroy an already existing
multiparty system and, for example, reduce to two the
number of parties in France or Italy. In any event, a
reform of this nature is inconceivable, because an
election determined by a majority vote on a single ballot
gives rise to unforeseen results when more than two
parties are involved. Yet in the German Federal Republic
and in Austria, such an electoral reform would very
likely hasten the trend, already underway, toward a
two-party system. Above all, it would prevent any move in
the opposite direction by posing a serious obstacle to
possible splits within the two major parties, and would
also discourage the revival of small political
parties.
Maurice Duverger, "Factors in a Two-Party and
Multiparty System,"
in Party Politics and Pressure Groups
(New York: Thomas Y. Crowell, 1972), pp.
23-32.