"The Senate of the United States shall be composed of two Senators from each State, chosen by the Legislature thereof for six Years...."
James Madison, Federalist No. 39:
"The House of Representatives will derive its powers from the people of America; and the people will be represented in the same proportion, and on the same principle, as they are in the legislature of a particular State. So far the government is national, not federal. The Senate, on the other hand, will derive its powers from the States, as political and coequal societies; and these will be represented on the principle of equality in the Senate, as they now are in the existing Congress. So far the government is federal, not national."
The Seventeenth Amendment to the U.S. Constitution, ratified 1913:
"The Senate of the United States shall be composed of two Senators from each State, elected by the people thereof, for six years...."
America's Party Platform:
"We also call for the repeal of the Seventeenth Amendment. Its enactment greatly reduced the power of our state legislatures and state governments – which are much closer to the people – and damaged our system of federalism."