ECONOMY

keith krehbiel 225
Conventional wisdom is meant to be challenged, and few if any scholars of the US
political system have amassed a more impressive set of challenges to received wisdom
than David Mayhew. In his 1991 tour de force Divided We Govern,Mayhewexecuteda
novel, laborious, and deeply insightful research design to address the question: does
it matter much whether the government is divided or unified? In terms of passing
major legislation (coded subjectively but convincingly), the answer was an emphatic
“no.” Governing regimes in US politics invariably need to exert substantial effort to
overcome various obstacles to policy-making, but, as an empirical matter, this is true
in unified as well as divided government. Moreover, when the natural propensity
for gridlock is overcome, the winning coalitions credited for such achievements
are almost invariably larger than minimum majority in size and thus bipartisan in
composition.
In this context, two stylized facts served as the impetus for the development
of the pivotal politics theory of law-making. First, why is gridlock common and
seemingly independent of party control? Second, why, when gridlock ceases to exist,
are winning coalitions large and bipartisan? The answer offered by pivotal politics
theory fits in a nutshell with room to spare: super-majoritarianism. Its concrete
manifestations and analytic characterizations are somewhat more intricate but, nevertheless,
can be made transparent to anyone with a basic grasp of spatial voting
models.
Borrowing from median voter theory, the pivotal politics model postulates that,
for any given issue the government may consider, a single, primary dimension is
sufficient for representing decision-makers’ essential conflicting interests. Formally,
each player (legislators in a unicameral law-making body plus a president) has symmetric,
single-peaked preferences over a unidimensional policy space, x ∈ R. These
assumptions on preferences have been common, beginning with the median voter
theory and extending through the important movement of “new institutionalism”
pioneered by Shepsle (1979) and his colleagues (e.g. Denzau and Mackay 1983; Shepsle
and Weingast 1987). Also common has been the assumption that, on any given
dimension, there exists an exogenous status quo point, q, which represents the policy
outcome in the event that the players of the game fail to come to an agreement on the
new policy, x.
The pivotal politics theory deviates from its predecessors in its specification of
voting rules. A noteworthy feature of the US Senate is its conferral, first by precedent
and eventually codified in its standing rules, of the right of any of its individuals to
engage in “extended debate,” i.e. to filibuster. Depending upon the period of history
studied, such rights effectively raised the voting threshold for law-making activity
from a simple majority standard of (n +1)/2 to a super-majority standard of 3/5 or
2/3. (For present purposes, we will confine attention to the contemporary case of
3/5 cloture.) Furthermore, the pivotal politics theory puts the president into the lawmaking
equation in a similarly super-majoritarian way. In this instance, the justification
lies in the US Constitution. The president’s signature is a sufficient condition for
policy change on any legislation Congress passes, but, in the absence of the president’s
signature, legislation either fails or requires a veto override by two-third majorities in
the legislative body.