Congress was given a bicameral structure by the framers. It was divided into two chambers: the Senate and the House of Representatives were to be elected in different ways and with different and sometimes overlapping powers, i.e. checks and balances.

The House of Representatives was designed as the popular, directly elected chamber. Its members are elected every two years, and in single-member constituencies - or districts - so as to ensure its responsiveness and answerability to the electorate. It can be regarded as the equivalent of the House of Commons in the UK. Every state was guaranteed at least one Representative or 'Congressman', but otherwise representation was based on the population of a particular state. To take account of population shifts, there was to be a process of reapportionment and - within each state - redistricting, every ten years following the census. 

The Senate is the upper chamber. It was intended to represent the individual states and have a more thoughtful and deliberative character. Through its six year terms of office, it would be - according to James Madison - the stable 'anchor' of Congress, thereby acting as a check on the more populist House and, at the same time, offering accumulated experience. A rolling system of election was adopted, so that one-third of the senate is subject to re-election every 2 years. This was established so as to ensure that the Senate would not surrender to the 'passions and panics of the moment' to which the House would be prone.