What was the cause and effect of John c calhoun threatened?

John C. Calhoun threatened to use nullification and secession as a response to federal policies he viewed as detrimental to Southern interests, particularly regarding tariffs and states' rights. This stance heightened tensions between the North and South, contributing to the sectional divide that ultimately led to the Civil War. His actions galvanized Southern support for states' rights and intensified the debate over slavery, influencing the political landscape of the time.