Bicameralism

The Constitutional Convention nearly broke apart over representation. Large states backed the Virginia Plan, apportioning both houses of a new legislature by population, and small states the New Jersey Plan, giving each state one equal vote. The Connecticut Compromise, adopted on July 16, 1787, created a House of Representatives apportioned by population and a Senate with two members per state. Equal Senate representation is the one feature of the Constitution that Article V protects from amendment without a state's consent.

The chambers differ by design. Representatives serve two-year terms and face voters often, while senators serve six-year staggered terms meant to provide stability. Revenue bills must originate in the House. The Senate alone confirms nominees and approves treaties. The House impeaches and the Senate tries impeachments. Every law must pass both in identical form, which the Supreme Court enforced in INS v. Chadha in 1983 when it struck down one-chamber vetoes of executive action.

Bicameralism slows lawmaking and gives small states outsized weight. Wyoming and California each elect two senators, though California has roughly 68 times as many people, so a Senate majority can represent a minority of the population. Defenders argue that the Senate protects federalism and smaller states and forces broader consensus. Forty-nine states also have two-chamber legislatures. Nebraska is the exception, with a single nonpartisan chamber since 1937.