What political tool emphasizes that the U. S. Constitution and acts of Congress, as well as U. S. treaties, must prevail over state constitutions and laws enacted by state legislatures?

Supremacy Clause.

Explanation:

Supremacy Clause is mentioned in the Article fourth, paragraph second and specifies federal law prevail over state laws. It forbids states from intervening with the constitutional powers by the central government, and from taking on any functions that are entrusted specifically to the federal government. This states that State laws are bound by the supreme law.