The Southern white political establishment evaded the spirit of these two amendments by passing laws that appeared to be neutral but were actually meant to take rights away from African Americans.
The 14th Amendment made African Americans legally equal to white people. It said that all Americans had to enjoy the “equal protection of the laws.” Southern whites evaded this by making laws that, on their face, were not anti-black. Instead, these laws (known as Jim Crow laws) appeared to constrain whites as much as blacks. Blacks could not use white drinking fountains, for example, but neither could whites use black drinking fountains. The white political leaders were able to say that this maintained equality (because everyone’s drinking fountains were allegedly equal) when the real point of the law was to discriminate against blacks.
The 15th Amendment protected blacks’ right to vote. Here, the leaders used things like literacy tests and poll taxes that were not explicitly based on race. These laws were meant to prevent blacks from voting, but they did not actually say that blacks could not vote. Thus, the leaders took away black rights without appearing to do so.
Thus, the leaders subverted the spirit of these amendments because the amendments were meant to make blacks and whites truly equal with one another.