Constitutional voting amendments were worthless without enforcement against southern disfranchisement.

Evidence

In the South, where most African Americans lived, the early part of the century was the high noon of white supremacy. Blacks in the South had no real political power. They had no voice in running the southern states. They had no mayors, no judges, no jurors. The Thirteenth Amendment had abolished slavery, and the Fifteenth Amendment gave African Americans the right to vote. But the Constitution was, insofar as black voting was concerned, nothing but a piece of parchment on display in a museum. Southern whites did not want blacks to vote, and they used every trick in the book to make sure black people could not vote at all. — Lawrence M. Friedman, A History of American Law, 3889