United States Supreme Court Cases
Dual representation. Bicameral state legislatures are no longer necessary for representational purposes, because the courts now require that the members of both houses be elected from equal population districts. In earlier times, bicameral state legislatures may have served a representational purpose: during the period of the American revolution, in some states the two houses represented somewhat different socio-economic groups; 50 years ago, members of the two houses of state legislatures represented somewhat different political communities (e.g., counties, cities, city wards). The two houses of Congress continue to represent different constituencies (state districts and population districts). But in state legislatures today, the members elected to the two houses are essentially duplicate representatives of the same population districts. Therefore, bicameral state legislatures can no longer be justified on representational grounds.*
In 1965, the Maine Constitution was amended to conform to the United States Supreme Court decisions. In 1968, the first Senate elections in Maine were held based on newly formed district populations. Prior to 1968, Senators were elected by counties.
* Source: www.house.leg.state.mn.us/hrd/issinfo/ini_bicam.htm