The 17th Amendment killed Federalism
Well, not really. The expansion of Federal power at the expense of State’s rights, is a story that dates back nearly as far as the Constitution itself. However, my hypothesis is that the 17th Amendment was a sort of first nail in the coffin, a point of no return for the federal power increase (and do note, this is just a political hypothesis).
To jog your memory from high school history class, the 17th Amendment was the one which called for direct election of Senators. Prior to this amendment, Senators were chosen by the State legislatures, while House Representatives were elected directly by the people. This makes a lot of sense when considering the design of the bicameral Congress. The House of Representatives was supposed to represent the People. Meanwhile, the Senate was supposed to represent the States.
This goes beyond just the idea that every state gets equal votes in the Senate. The Senators were directly selected by the State legislatures, and thus were accountable to them. In the past, Senators would likely block bills encroaching on State government’s powers, because they depended on the State legislatures for re-election.
But enter the 17th Amendment.
By switching to direct election of Senators, the entirety of Congress now is a conduit directly for the people. State governments don’t have any representation in the Federal government anymore, and thus no one to fight for preserving their constitutional powers. No federal politicians have their job hanging on the line for not pissing off the State governments.
I feel many people think of the 17th Amendment as one of the “well, duh, that’s obviously good” amendments, because it “increases democracy”. But it’s important to think through the mechanism design that the framers put into the Constitution.