[184] Although he criticized those who sought to limit or end slavery, he rarely rebuked southern politicians who took extreme positions or opposed northern interests.[185]
David Potter concludes that the Ostend Manifesto and the Kansas–Nebraska Act were "the two great calamities of the Franklin Pierce administration  ... Both brought down an avalanche of public criticism."[186] More important, says Potter, they permanently discredited Manifest Destiny and "popular sovereignty" as political doctrines.[186] Historian Kenneth Nivison, writing in 2010, takes a more favorable view of Pierce's foreign policy, stating that his expansionism prefaced those of later presidents William McKinley and Theodore Roosevelt, who served at a time when America had the military might to make her desires stick. "American foreign and commercial policy beginning in the 1890s, which eventually supplanted European colonialism by the middle of the twentieth century, owed much to the paternalism of Jacksonian Democracy cultivated in the international arena by the Presidency of Franklin Pierce.