Politics, Policy,
and Organizations
either coalition party, the Core would still span just the ideal points from
L
2
to G
2
: there exist proposals that could upset an SQ lying to the left of
L
2
with the support of L
2
, L
3
, and G
1
, G
2
, and G
3
(these
five members
comprise a parliamentary majority); similarly, there exist proposals that
could upset an SQ lying to the right of G
2
with the support of L
1
, L
2
, L
3
,
and G
1
and G
2
(who comprise a parliamentary majority). So the possi-
90
Fig. 5. A party coalition unicameral parliament without perfect coalition party
discipline
bility of defection could still produce a Core that is the same size as when
defection is not possible (compare the identical Core in
fig. 4A).
6
If the governing coalition includes only a bare majority of the cham-
ber’s members, as in
figure 5A, the resulting Core will span the ideal
points of all the members of all the parties in the coalition. In this case,
the size of the Core will depend on the distance between the “outermost”
members of the two “outermost” parties in the coalition: the farther
apart are these outermost members the larger the Core. In
figure 5A, for
example, the size of the Core hinges on the distance between L
1
and G
2
.
At the other extreme, if the coalition includes almost all the members
of the entire chamber, then the size of the Core might span only the ideal
points of the median members of the two outermost parties in the coali-
tion. In
figure 5C, for example, the governing coalition includes eight of
the nine members of the parliament. The Core here spans the ideal
points of L
2
and G
3
, the relevant (e.g., outside) median members of the
two outermost parties. While these
first three examples show Cores of
substantial size, if the ideal points of these two parties were to overlap
suf
ficiently a single-point Core could be produced, as in figure 5
D.
Overall, then, if the parties in the coalition lack perfect discipline the
Core will span at least the ideal points of the median members of the two
outermost parties in the coalition and the Core may grow larger as the
size of the coalition decreases. And, of course, the size of the Core will
depend on the distance between the relevant members of the two outer-
most parties in the coalition: the closer together their ideal points the
smaller the Core.
A Party-Free Bicameral Parliament
Next we consider a bicameral parliament consisting of two chambers, to
be called the House and Senate. In this system, some status quo policy
can be upset whenever a majority of the House and a majority of the
Senate can agree on some other policy; each chamber has authority to
block efforts by the other to change policy. Our goal is to determine the
set of equilibrium policies in this bicameral system. We assume there are
no parties. Since there are no parties, questions of party discipline, mo-
nopoly agenda control authority, and so forth are moot.
We begin with the same nine actors used previously, constructing a
model of a bicameral parliament in which the nine individuals are parti-
tioned into a four-member Senate and a
five-member House (see fig. 6A).
Veto Points in Democratic Systems
91
Politics, Policy, and Organizations
Note that three senators constitute a bare majority of the four-member
Senate and three representatives constitute a bare majority of the
five-
member House.
Finding the equilibrium policies in a bicameral parliament is similar
to what occurs when there are two parties in a coalition in a unicameral
parliament. First, for each SQ lying to the left of S
2
in
figure 6
A there ex-
ists some proposal to upset this SQ, which would gain the support of
three of the four Senate members (S
2
, S
3
, and S
4
, who comprise a Senate
majority) and all
five House members. But now consider an SQ lying be-
tween S
2
and S
3
: there exists a proposal to replace this SQ with a policy
on or to the right of S
2
, which would be supported by S
3
and S
4
and by
all the House members, but S
1
and S
2
would reject this proposal. Since this
proposal would not be supported by a majority of the Senate (three votes
are needed for this), the proposal would fail. The same logic holds for
status quo policies lying to the right of H
3
. Hence, the proposal would
fail for lack of a House majority. The result is that the points spanned by
the line from S
2
to H
3
are in equilibrium; hence, all these points from S
2
to H
3
comprise the Party-Free Bicameral Core.
92
Fig. 6. A party-free bicameral system