"Mexico is to us the forbidden fruit"

On May 15, 1846, three days after the Senate effectively authorized war against Mexico over his objection, John C. Calhoun wrote to fellow South Carolinian Henry W. Conner a letter in which he apparently alluded to the underlying source of his concern. "Mexico," Calhoun warned, "is to us the forbidden fruit; the penalty of eating it [is] to subject our institutions to political death."

Three months later, David Wilmot introduced his famous proviso.