Final answer:
John C. Calhoun is associated with the phrase 'states' rights' because he defended the rights of the South and argued for the concept of states' rights. He believed that individual states should have the power to check the authority of the federal government, and he advocated for a concurrent majority.
Step-by-step explanation:
John C. Calhoun is often associated with the phrase 'states' rights' because he was a leading political theorist defending the rights of the South and slavery.
He believed in the concept of states' rights, which meant that individual states should have the power to check the authority of the federal government. Calhoun argued for the idea of a concurrent majority, where a region could veto or disallow legislation put forward by a hostile majority.