The bicameral design of the U.S. Congress is consistent with the basic principle of government embraced by the framers of the U.S. Constitution: that government divided into units which must share power with one another provides an inherent check against tyranny. The division of the Congress into two chambers to avoid legislative despotism emanates from this principle.

The House, with its entire membership standing for election every two years, is considered the chamber closest to the electorate. Running for re-election virtually constantly means that Representatives come to know their constituents well, and therefore are more likely to reflect accurately the views of the local citizenry and advocate the needs of their districts. They are also more likely to be sensitive to changes in popular sentiment. However, it was feared that these same characteristics might also lead to a short-term view of what constitutes good public policy.

In contrast, the Senate was designed to protect against the popular passions of the moment. Senators stand for election every six years. Moreover, the Senate is a continuing body; only one-third of its membership runs for re-election at any one time. This continuity and the longer term are meant to enable Senators to resist the pressure of immediate popular opinion and be able to serve as a restraining influence -- or a court of appeals -- for House action. The framers expected Senators to be older, wiser, and more deliberative than Representatives and thus able to offer a long-term view of what makes good public policy.

Although likely to be apocryphal, a famous simile for this is reputed to have been voiced by George Washington to Thomas Jefferson when the latter criticized the need for a second chamber. "Why," asked Washington, "did you pour that coffee into your saucer?" "To cool it, " replied Jefferson. "Even so," said Washington, "we pour legislation into the senatorial saucer to cool it."

Under the U.S. Constitution, the two chambers are as equal. Both must give their consent to the enactment of a law. Colloquial references to the two as an "upper body" and "lower body" are misnomers, arising from the fact that when Congress first met in New York City (as well as later in Philadelphia), the Senate chamber was located a floor above the House.

The Constitution does give certain exclusive powers to each chamber. Nominees chosen by the President to serve as judges, ambassadors, cabinet officers, and senior executives must be confirmed by the Senate. Treaties negotiated with foreign nations must be ratified by the Senate. The House has no formal role in either process. However, the House is given the authority to originate all revenue (tax) bills, and through historical precedent this has been extended to all appropriations (spending) bills as well. The Senate has full opportunity, though, to debate and modify the legislation sent over by the House and, as with all bills, the full concurrence of both chambers is necessary for the legislation to progress.