D. Ingberman et J. Villani, AN INSTITUTIONAL THEORY OF DIVIDED GOVERNMENT AND PARTY POLARIZATION, American journal of political science, 37(2), 1993, pp. 429-471
This paper develops a simple model of institutionally driven party com
petition which may explain the persistence of divided government. In t
he basic model, two parties that are solely motivated to win elections
compete for two offices, the legislature and the executive. Parties o
ffer positions in a single dimension to a single-district sophisticate
d electorate that understands the institutionally defined relationship
between electoral and policy outcomes. When parties are risk-averse,
competition for the two offices leads to a prisoner's dilemma: the par
ties can jointly improve on the one-shot Nash equilibrium in which the
y adopt convergent positions. Several extensive form election games ar
e shown to allow the parties to solve their prisoner's dilemma in a su
bgame-perfect Nash equilibrium. In such an equilibrium, parties adopt
widely separated positions, and divided government and split-ticket vo
ting occur with high probability. Unlike typical voting models, in the
basic model there is no tendency for electoral equilibrium to produce
the (expected) median voter's ideal policy outcome. These results are
robust to a variety of extensions, including significant sincere voti
ng, multiple policy dimensions, and defections by incumbent candidates
.