Under the original design of the US Constitution, the House and Senate were distinct bodies with distinct functions. The House represented the people as a whole and the Senate was designed to represent the various state Legislatures. In this way, the people as a whole would be represented and the States would be able to ensure that the federal government would not encroach on the power of the states or grow too powerful compared to the states. How? Originally, it was the state legislatures that would elect the senators and send them to Washington.
The Senate will be elected by the state legislatures, and represent the states in their political capacity; and thus each branch [the House and the Senate] will form a proper and independent check on the other, and the legislative power will be advantageously balanced.”
Charles C. Pinckney – Early American statesman of South Carolina, Revolutionary War veteran, and delegate to the Constitutional Convention.
The Representatives are to be elected by the people at large. They will therefore be the guardians of the rights of the great body of the citizens. So well guarded is this Constitution throughout, that it seems impossible that the rights either of the states or of the people should be destroyed.
Oliver Wolcott – Signer of the United States Declaration of Independence and also the Articles of Confederation as a representative of Connecticut.
When did this change? This changed when the 17th Amendment to the Constitution was passed in 1913. Why did it pass? The Progressive movement. Progressives across the country were clamoring for the popular election of the senate (no doubt because like the Supreme Court of today, the Senate of their day was blocking the Progressive Agenda). Out of fear that the desire for that change in the Constitution would lead to an outright constitutional convention where the whole of the constitution could be scrapped, the proposal was made in the congress and was ratified by the states. The old Senate was no more and the new Popularly Elected Senate was created. Speaking of the senate…
… so there are particular moments in public affairs, when the people stimulated by some irregular passion, or some illicit advantage, or misled by the artful misrepresentations of interested men, may call for measures which they themselves will afterwards be the most ready to lament and condemn. … What bitter anguish would not the people of Athens have often escaped, if their government had contained so provident a safeguard against the tyranny of their own passions? Popular liberty might have then escaped the indelible reproach of decreeing to the same citizens, the hemlock the one day, and statues the next.
James Madison, Federalist No.63
Are we better off for the change today? Have the states (state governments ie. legislatures) maintained a form of representation in the Federal Government? Has the Federal Government kept itself from infringing on the liberties of individuals?