Hvg krause 47K. qxd

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

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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 5D.

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

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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 6A 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

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