The representational differences between the House and Senate stem from the different term lengths, qualifications for office, and electoral constituencies defined in the Constitution.
Voter and Member Qualifications in the House of Representatives
Article I, Section 2, Clause 1 states that members of the House shall serve two year terms and “the electors in each state shall have the qualifications requisite for electors of the most numerous branch of the state legislature.” Under Article I, Section 2, Clause 2, members must “have attained the age of twenty-five years, and been seven years a Citizen of the United States, “ and “…when elected, be an inhabitant of that State in which he shall be chosen.”
Although Madison thought it was difficult to determine exactly how long a term is best for members of the House, experience in state legislatures had shown that a term of one year or less was too short. He thus refuted the Anti-Federalist claim that “where annual elections end, tyranny begins.” (Federalist, No. 53) The two-year term length met the essential criterion of being “frequent” enough for a republican form of government while also allowing representatives to gain the experience needed to gain the “practical knowledge” to perform their service. In Federalist, No. 52, Madison writes: “As it is essential to liberty that the government in general should have a common interest with the people, so it is particularly essential that the branch of it under consideration should have an immediate dependence on, and an intimate sympathy with, the people. Frequent elections are unquestionably the only policy by which this dependence and sympathy can be effectually secured.” Popular elections to the House were an essential part of the checks on governmental power: “A dependence on the people is, no doubt, the primary control on government…”
Madison explained that using state constitutional guidelines for identifying electors was “the best that lay within their [the States] option.” (Federalist, No. 52) The states would not accept, and the Convention delegates could not have settled upon, a “uniform rule” for electors from every state. At the same time, since the qualifications of electors are “fixed by the State constitutions, it is not alterable by the state governments, and it cannot be feared that the people of the states will alter this part of their constitutions in such a manner as to abridge the rights secured to them by the federal Constitution.” (Federalist, No. 52)
Both the age limit and number of years as a citizen were proposed at the Convention by George Mason of Virginia and settled upon after a modest debate. During ratification, Madison pointed out that those minimum and uniform qualifications left plenty of room for a wide range of talented individuals to be elected to the House: “Under these reasonable limitations, the door of this part of the federal government is open to merit of every description, whether native or adoptive, whether young or old, and without regard to poverty or wealth, or to any particular profession of religious faith.” (Federalist, No. 52)