ECONOMY

8 introduction: the reach of political economy
Given the assumption of how legislators choose parties, nearly all legislators from
theleftpartyvotefortheproposal;whilemostofthoseoftherightpartyvoteagainst
it. Indeed, if the status quo is not too far to the right relative to the distribution of
legislature preferences, then most of the members of the right party will vote against
the change. In other words, voting on this legislature will exhibit polarization by party
even though the party exerts no pressure on its members to vote one way or another.
Alessonofthismodelisthatpolarizedpartyvotingcanemergeasthecombined
result of legislative preferences and sorting into parties without being a function of
any legislative institutions that advantage parties or that constrain member behavior.
Although this approach rationalizes only minimalist legislative institutions, it
provides an important baseline from which to judge other models. While most
approaches rely on legislator preferences to some degree, we term this approach a
preference-based approach because it relies solely on legislative preferences and the
median voter model to explain political phenomena, such as polarized party voting.
1.2 Committees as Commitment Devices
The second approach is exemplified by Weingast and Marshall’s (1988) “Industrial
organization of Congress.” This approach built on previous theoretical and empirical
work. Going back to Buchanan and Tullock (1962), many models of legislative choice
emphasized logrolling and vote-trading. By logrolling and trading votes, members
and the districts they represented were better off. Logrolling can thus be seen as a
legislative institution parallel to market institutions in the economic sphere.
Empirically, the substantive literature on Congress emphasized the central importance
of committees, which were seen to dominate the policy-making process. That
literature emphasized committee specialization and self-selection onto committees
by members most interested in the committee jurisdiction (Fenno 1966, 1973; Shepsle
1978). Clearly, this form of committee organization suited members’ electoral goals
(Mayhew 1974). So committee organization was seen as reflecting the preferences of
the legislators and their constituents. In this view, the key to understanding legislative
organization was legislative exchange.
Weingast and Marshall sought an explanation of congressional organization that
accounted for the fundamental features then found in the substantive literature. They
based their approach on two observations: first, the legislature faced many different
issues that cannot be combined into a single dimension: agriculture is not commensurate
with civil rights, banking, or defense. Second, vote-trading had significant enforcement
problems as a means of legislative exchange. For example, suppose that one
group of legislators seeks to build dams and bridges, another group seeks regulatory
control of some market, and that neither group alone comprises a majority. The two
groups could, per logrolling, agree to support one another’s legislation. But this raises
a problem: once their dams and bridges are built, what stops those receiving them
from joining those locked out of the original trade to renege on the deal by passing