Puerto Rico had an “Anne Heche moment” today when voters approved a referendum that may eventually lead to another referendum that would amend the commonwealth’s constitution to get rid of one house of the legislature and create a unicameral Legislative Assembly starting in 2009.

While in the post-Wesberry v. Sanders era (the real “one man, one vote” case, rather than its predecessor Baker v. Carr) the existence of upper houses can be viewed as a vestige of an earlier era, nonetheless 49 states have retained an upper house, partly for reasons of inertia, but also (perhaps) taking heed of counsel from James Madison in Federalist 51:

In republican government, the legislative authority necessarily predominates. The remedy for this inconveniency is to divide the legislature into different branches; and to render them, by different modes of election and different principles of action, as little connected with each other as the nature of their common functions and their common dependence on the society will admit. It may even be necessary to guard against dangerous encroachments by still further precautions.

State governments in general tend to be more legislature-dominant than the federal government—members of the judiciary in most states have to run for reelection, circumscribing their freedom of action, while the executive branch in many states is comprised of various (often competing) elected officials rather than a single governor heading an appointed cabinet—so the argument for Madison’s position in the case of states is rather sound.

þ: Steven Taylor, who notes a “pernicious Nebraska influence” going on here.