Which amendment significantly advanced the power of the federal government over states?

The Fourteenth Amendment is significant because it fundamentally altered the relationship between the federal government and the states, particularly through its Equal Protection and Due Process Clauses. Originally ratified in 1868, the amendment was designed to address issues related to former slaves after the Civil War, but its implications extend far beyond that era.

The Due Process Clause prohibits states from depriving any person of life, liberty, or property without due process of law, effectively ensuring that states must adhere to certain fundamental rights and protections that the federal government guarantees. The Equal Protection Clause mandates that no state shall deny to any person within its jurisdiction the equal protection of the laws, which has been pivotal in advancing civil rights and ensuring that state laws cannot discriminate against individuals.

Through numerous Supreme Court rulings, the Fourteenth Amendment has been used to apply federal protections at the state level, leading to increased federal oversight in areas such as education, voting rights, and civil liberties. This amendment has served as a basis for substantial judicial decisions that expanded the federal government's authority, thereby diminishing the autonomy of states in various aspects of governance.