Okay. Here's the scoop as I understand it:
Calhoun believed that if a State thought that a Federal Law was passed that was immormoral or would cause undue harm to a certain State, that State was within the rights of the Constitution to "nullify" (ignore) a law--even though it had been passed by the Federal Government as the law for the Entire Country.
The Confederacy was hardly the first time a group of States seriously considered seceeding from the Union and forming their own country. When WAS the first time that happened?
"I say YOU'RE the CUTEST one. No, I say YOU'RE the CUTEST One. And we go on like that from dawn to three."