ABSTRACT
Legislative scholars work under the assumption that legislative party cohesion
is a prerequisite or at least highly conducive to legislative success. Certainly in
a parliamentary system, the majority party or governing coalition is more
likely to enact its legislative proposals into law if it maintains high unity of
action among party members. In a presidential system, however, the relation-
ship may be more complex. In the United States, for example, the same
party may not control the two houses of the legislature and the presidency.
And even when control is unified, the congressional party and the president
may not always agree. Consequently the president may sometimes have to
rely on the opposition party for support.1
